Activate 60 days premium free antivirus

How do i select a device so i can activate the antivirus.
I get this message: “Your subscription isn’t being used on any device”.

First, I’m an Avast user and not an Avast Team member. I also only use Avast Free Antivirus.

When you did this presumably you would have had to sign up for the trial, which would have entailed creating an avast account.