Quick answer: Open Muse and look for the Invite entry (top right of the main screen in current versions). Your personal 6-character code is shown there. Other people redeem your code in their Settings; every qualifying redemption earns you 1 billion tokens, up to roughly 20–30 redemptions (20–30 billion tokens).
Two different things look similar:
If you copied a code from a website or a friend, that is not your code — do not re-share it as yours.
Your invite screen shows your completed redemptions and your cap. Check it before a big share push: if your code is already full, people who try it will only hit an error — and a code that keeps failing in public gets ignored fast.
Most shared codes are copied but never redeemed, because the message forgets the two things that matter: the 48-hour deadline and the exact path. Send both, together:
Here is my Muse invite code: XXXXXX Redeem it within 48 hours of creating your Muse account: Settings → Redeem token (app) or Settings → General → Usage → Redeem invite code (web). We each get 1 billion Muse tokens.
Submit your code on the fill-up page. New users claiming codes here are served open fill-up orders first, and you can watch the hand-out count grow. It is free to submit, and it runs alongside your own sharing.
Submit my code for fill-up