Need to change original user's email and password to ours.

We need to change the original user's email and password so we can update the settings and be able to use our PBS icon. We gave this AppleTV to a close friend as a Christmas present, but he doesn't want it. We have been using for about a year, but to updates settings it keeps asking for the password to his old email, which he doesn't have anymore and can't remember the pasword for it anyway.

So how can we get rid if it being his email and password and change it to just one of ours?