Avast antiviruses offer complete protection against all cyber threats and infections. Get free or paid Avast antivirus. Download, install, and activate it from avast.com/activate. To activate Avast Pro Antivirus with an activation code: Right-click the Avast icon in your system tray and choose Subscription information. On the My licenses screen, click Enter a legitimate activation code. Type or paste your activation code into the text box and click on Enter. Check your license details for the entered activation code.