Thanks, your credits are on the way.

Three steps

1. Find your licence key. It is in the email from Polar (subject contains "Smart Filter"), or in the Polar customer portal. It starts with SF-.
2. Open Smart Filter. Click the puzzle piece in Chrome's toolbar, then Smart Filter (or its icon, if you pinned it).
3. Enter the key. Click "Enter key", paste the key and click Activate. The popup names your plan and your credits.

Credits appear within a minute. Plans add credits every billing cycle, and credits never expire. A top-up bought with your plan's email needs no key: its credits join your plan's balance on their own. On a plan and no new credits after a minute? You may have paid with a different email: open Smart Filter's settings, go to Account, click "Change key" and paste the key to see what to do.