docs: Add Git LFS installation note

docs/CONTRIBUTING.md

@@ -26,6 +26,9 @@ cd namesake
 pnpm install
 ```
 
+> [!NOTE]
+> Cloning the repo requires Git LFS (Large File Storage), see [install instructions](https://docs.github.com/en/repositories/working-with-files/managing-large-files/installing-git-large-file-storage).
+
 ### Connect to Convex (first time only)
 
 The first time you set up the app, you'll need to connect to our backend service, [Convex](https://www.convex.dev/). Run:
@@ -67,6 +70,24 @@ pnpm dev
 
 The app should now be available at http://localhost:5173. You're all set up!
 
+### Register a local Namesake account
+
+Upon opening your app at http://localhost:5173 you will be greeted with a login form. To login, you will need an account. Currently, registering requires an early access code. To generate a code for your local Namesake instance:
+
+1. Open your [Convex dashboard](https://dashboard.convex.dev)
+2. Navigate to your Namesake project
+3. Click into the "Data" tab
+4. Select the `users` table
+5. Copy the `_id` of any user
+6. Switch to the `earlyAccessCodes` table
+7. Click the "+ Add Documents" button
+8. Paste the `_id` in the `createdBy` property and click "Save"
+9. Copy the `_id` of the newly created document
+10. Return to your local app
+11. Select the "Register" tab
+10. Paste the `_id` into the "Early Access Code" input
+11. Register an account
+
 Now that the development app is running, let's get familiar with what's inside.
 
 ## Project structure