diff --git a/docs/5-build_skills.md b/docs/5-build_skills.md
index ed573ec..9b76326 100644
--- a/docs/5-build_skills.md
+++ b/docs/5-build_skills.md
@@ -36,4 +36,97 @@ The second tab of the addon will follow these [designs](./build_skills_tab_desig
 ---
 
 ## Implementation Plan
-TODO
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+
+### 1. Add a `SaveSkills` function to Data.lua
+- Create `AltSystem.Data:SaveSkills(editedSkills)` that writes skills back to the TRP3 profile
+- Access the TRP3 profile via `TRP3_API.profile.getData("player/characteristics")` to get the `characteristics.PS` (personality traits) array
+- For each edited skill, update or insert entries in `PS`:
+  - `LT` = skill name
+  - `RT` = level keyword (e.g. "Novice", "Adept", etc.)
+  - `V2` = numeric value (0–20)
+  - `IC` = preserve existing icon (do not change); for new skills, use a sensible default icon (e.g. `"inv_misc_questionmark"`)
+- Remove any PS entries that were deleted by the user
+- After writing, call `TRP3_API.dashboard.showCharacteristics()` or fire the appropriate TRP3 event if needed to refresh TRP3's own UI
+- **Edge case:** If the TRP3 API is unavailable, show a warning message and abort save
+
+### 2. Extract skill-level constants into shared lookup tables in Data.lua
+- The acceptance criteria defines value ranges per level (Inept: 0, Novice: 1–5, Adept: 6–10, Expert: 11–19, Master: 20)
+- `SKILL_KEYWORD_RANGES` already exists but excludes Inept/Master min-max correctly for the Build tab's needs; extend or create a new table `AltSystem.Data.SkillValueRanges` that is accessible from UI.lua:
+  ```
+  { Inept = {min=0, max=0}, Novice = {min=1, max=5}, Adept = {min=6, max=10}, Expert = {min=11, max=19}, Master = {min=20, max=20} }
+  ```
+- Create `AltSystem.Data.SkillLevelOrder` — an ordered array `{"Inept", "Novice", "Adept", "Expert", "Master"}` for populating the level dropdown in display order
+- Create a helper `AltSystem.Data:GetDefaultValueForLevel(level)` that returns the minimum value for that level (used when the user changes level to auto-set the value)
+
+### 3. Add a function to read raw skills (with numeric values) from TRP3 in Data.lua
+- Currently `RefreshSkills()` converts TRP3 traits into `{name, level, modifier}` — the Build tab needs the raw **numeric value** and the **icon** as well
+- Create `AltSystem.Data:GetEditableSkills()` that returns an array of `{name, level, value, icon}` for each valid skill trait in the TRP3 profile (excluding Base Roll and Unskilled, which are system-generated entries)
+- Sort the returned skills by level using `AltSystem.Data.SkillLevelOrder` ordering (Inept first, Master last) — matching the acceptance criteria "sorted by level"
+- Reuse existing helpers `FindSkillKeyword` and `ParseSkillLevel` (promote them from local to module-level if needed, or call internally)
+
+### 4. Build the Build Skills tab UI (new file: BuildSkillsUI.lua)
+- Create a new file to keep UI.lua manageable; register it in `AltSystem.toc` between `UI.lua` and `Roll.lua`
+- Create `AltSystem:CreateBuildSkillsContent(parentFrame)` called from `CreateMainFrame` in UI.lua (replacing the placeholder)
+- **Layout structure:**
+  - **Info text** at top — two golden/yellow paragraphs explaining that skills come from TRP (matches mockup)
+  - **"Skill list" section header**
+  - **Column headers**: Name, Level, Value (bold golden text)
+  - **Scrollable skill list** — a `ScrollFrame` containing dynamically created skill rows
+  - **"Add A Row" button** — anchored below the last skill row, inside the scroll child
+  - **"Save Skills to TRP" button** — pinned/sticky at the bottom of the tab, outside the scroll frame
+
+### 5. Implement editable skill rows
+- Each skill row is a frame containing:
+  - **Name**: `EditBox` (text input) — pre-filled with current skill name
+  - **Level**: `DropdownButton` (WowStyle1DropdownTemplate) — options: Inept, Novice, Adept, Expert, Master
+  - **Value**: `DropdownButton` — options dynamically generated based on selected level (e.g. Novice → 1,2,3,4,5)
+  - **Delete button**: A button with a trash-can icon/red texture that removes the row
+- Store all row data in a local working copy array (`editableSkills`), not directly in `AltSystem.Data.Skills`
+- When the **level dropdown** changes:
+  - Update the value dropdown options to only show valid values for the new level
+  - Auto-set the value to the minimum for that level (e.g. switching to Adept → value becomes 6)
+- **Row management:**
+  - `CreateSkillRow(parent, index, skillData)` — creates or recycles a row frame
+  - `RefreshSkillRows()` — rebuilds/repositions all rows and updates scroll child height
+  - Deleting a row removes it from `editableSkills` and calls `RefreshSkillRows()`
+
+### 6. Implement "Add A Row" functionality
+- Clicking "Add A Row" inserts a new entry into `editableSkills`:
+  - `{ name = "Skillname", level = "Novice", value = 1, icon = "inv_misc_questionmark", isNew = true }`
+- Calls `RefreshSkillRows()` to render the new row
+- The scroll frame should auto-scroll to show the new row
+
+### 7. Implement "Save Skills to TRP" functionality
+- On click, call `AltSystem.Data:SaveSkills(editableSkills)` which:
+  1. Reads current `characteristics.PS` from TRP3
+  2. Rebuilds the PS array: keeps non-skill traits untouched, updates/adds/removes skill traits based on `editableSkills`
+  3. Writes the updated PS back to the TRP3 profile data
+  4. Calls `RefreshSkills()` so the Use Skills tab dropdown reflects the changes immediately
+- Show a confirmation message (print to chat or a brief on-screen text) on successful save
+- **Edge cases:**
+  - Empty skill list: allowed — just remove all skill traits from PS
+  - Duplicate skill names: allowed (TRP3 doesn't enforce uniqueness)
+  - Unsaved changes + tab switch: no confirmation dialog required (per spec, changes are just lost)
+
+### 8. Wire up tab switching to populate Build Skills tab
+- In `SelectTab(2)` (UI.lua), call `AltSystem:RefreshBuildSkillsList()` to reload skills from TRP3 into the working copy
+- This ensures the Build tab always shows the latest TRP3 data when opened, and any unsaved edits are discarded on tab switch
+
+### 9. Update AltSystem.toc
+- Add `BuildSkillsUI.lua` to the file list (after `UI.lua`, before `Roll.lua`)
+
+### 10. Testing checklist
+- [ ] Build Skills tab shows skills from TRP3 profile, sorted by level
+- [ ] Skill name is editable via text input
+- [ ] Level dropdown shows all 5 levels; changing level updates value dropdown options and auto-selects minimum value
+- [ ] Value dropdown only shows values valid for the current level
+- [ ] Delete button removes the row immediately
+- [ ] "Add A Row" adds a row with defaults (Skillname, Novice, 1)
+- [ ] Skill list scrolls when rows exceed visible area
+- [ ] "Save" button is always visible (pinned to bottom)
+- [ ] Save writes correct data to TRP3 profile (LT, RT, V2, IC preserved)
+- [ ] Save does not modify icons of existing skills
+- [ ] After save, Use Skills tab dropdown reflects the updated skills
+- [ ] Switching tabs discards unsaved changes and reloads from TRP3
+- [ ] Works correctly with 0 skills (empty profile)
+- [ ] Works correctly with many skills (20+) — scroll behavior
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