Getting most out of Avast Premium

My elderly father-in-law accidentally signed up for Avast Premium, after I put on the free version. I was going to apply for a refund and backload to the free version, but then he said "Maybe it’s better with all the porn sites I look at " !! No, he wasn’t kidding.
So, I’ve never used the premium version. What should I do to make sure it is set up as secure as possible for an elderly, computer-illiterate, porn-loving great-grandpa?
Thanks

https://help.avast.com/en/av_free/19/