So I accidentally checked the hide button on a topic and posted it, thank you laggy computer, and I'm wondering how to un-hide it? Sorry if it's a dumb question, I'm brand new to forums and stuff

When you click onto your hidden forum, at the bottom where the 'subscribe' options are, there'll be a little option that says 'publish'.
Click that and you'll be good to go.

Thanks so much for the help :')