Another computer i didnt buy appears under my account

So a friend of mine has bought avast on his computer. he didnt realize he put my email on there instead of his, but he payed and put his address and information on it. Its currently under my account, how do i remove it so he can access it through his own account or how do i pass it on to him so it wont appear on my account but on his?

He just needs to logout from your account in his installation of Avast and login with his email. The device will be automatically unpaired from your account and paired to the new one.