Paste the two values from your Supabase project (Settings → API). They're stored on this device only, and the same two go on every device you want in sync.

Enter your email and pick a password. If you're new here, this creates your account — there's no email to wait for. Use the same email and password on every device you want sharing one list.

You're signed in. You just need to be added to the list.

Ask the person who shared this app to open ☁ → Sync & sharing and add your email.

Leave this open — it checks every minute and will start working on its own the moment they do. Nothing else for you to do.

Tap a category to grant or revoke it for that person. Changes save instantly.