On your Home screen, tap the Avast Cleanup icon to open the app, tap Get started ▸ Next, then select ⋮More options (three dots) ▸ Already purchased?.
Select Use an activation code.
Tap the text box below to copy your activation code, paste it directly into the app, then tap Use this code.
See detailed activation instructions
Type the activation code you received with the product into the text box, and tap Use this code(if asked, enter your name, email, and postal code).
See detailed activation instructions
To open the app, tap the Avast Cleanup icon on your Home screen.
That's it! Don't forget about installation on other devices.