I asked two Star Trek questions a while ago and I'm trying to comment back. For some reason I can't add a comment. Any help?
For commenting anywhere, you need 50 reputation points. (This equates to 5 upvotes on answers or questions, so you should be able to pick up those points fairly quickly if you have good content to contribute.)
For commenting on your own posts, or on answers to your own questions, there's no reputation requirement - you should be able to do this. If this is what you're trying to do and failing, then perhaps for some reason your account isn't associated with the questions you asked? I can only see one question in your account history, but you mention that you asked two. (Could you provide a link to the other one?) If you asked the questions using two different accounts and you need to merge accounts, you can do that by following the instructions here.
In general, the help centre has most of the info you need about the basic workings of the site, but you can always feel free to ask on meta if you still need help. (The main site is only for questions about sci-fi or fantasy; questions about the site should be asked here on meta instead.)