In order to redeem the code follow the instruction below:

Download Avast Premier from the Avast website.
Right-click the downloaded setup file and choose Run as administrator.
The Avast Setup wizard appears.- Click Install for setup with default options.- Select Custom installation to select the location of program files, and choose program components and languages on the following screen.
The installation progress bar appears while the program installs. When setup is complete, you can activate your subscription by clicking I have already bought a subscription or continue in 30-day trial mode.
When a network is detected, select a firewall mode.- Select Private if your computer is connected to a home or private network.- Select Public if connected to a public or shared network.
Avast Premier is now installed on your computer and ready to use.

Click here to check the official guide of activating Avast Ultimate