Members only commentators.

I want everyone to be able to view all posts and also all the comments on the various posts. But I want to permit only registered site members to post comments; and also there will be some criteria for membership (e.g. an “I agree to the terms and conditions” stipulation, as well as some sort of nominal donation). But I have no idea how to set this up properly. My URL is https://bibletruthchatroom.com/ Does anyone have any suggestions?