I wanted to respond to someone’s answer but don’t know how to tag them in my question! Any help?
Welcome to our site. First, you should take the tour to learn how the site works. It is a Q&A site, and not a forum, meaning a person asks a question, and receives answers only - no discussions should occur using an answer to post.
Second, I don't see any questions asked on your user. So I'm not sure what question you mean. It's also not possible to tag someone in a question or answer post. You can only tag someone in comments, (or technically also in a chat room). However, you cannot leave comments on posts except your own currently, since you lack the reputation needed to comment freely on all posts. You need 50 reputation to do that.
Once you have enough reputation, or you are commenting on one of your own posts, you can tag someone in a comment by typing an "at" symbol ("@") and then the users name. It's unnecessary to tag the original author of a post, since they will receive a notification regardless. You also cannot tag someone who has not commented on the same post. You can only tag those who have left a comment already, or anyone that has edited the post.
Comments are also meant to be used to ask for clarification or to clarify something, provide feedback in the form of constructive criticism, or to suggest additional information. They aren't meant to be used for discussion or general chatting.