On your Home screen, tap the Avast Mobile Security icon to open the app, select Get started, then choose Already purchased?(if you switched to a free version with ads, tap the Account icon in the bottom-right corner of the screen, then tap Upgrade Options ▸ ⋮More options (three dots) ▸ Already purchased?).
Type the activation code you received with the product into the text box, and tap Continue(if asked, enter your name, email, and postal code).
See detailed activation instructions
To open the app, tap the Avast Mobile Security icon on your Home screen.