We have a different process to install webroot with keycode which you can follow below one of the simplest ways.
Open the SecureAnywhere interface
Click the Webroot icon in the menu bar
Then select Open Webroot SecureAnywhere
From the main window, click the gear icon next to My Account.
Enter your new key code in the box on the right.
Click webroot activation key.
If you are unable to find this helpful then do follow here for more step by step instruction to use webroot antivirus activation code.