um, i wrote a harry potter rap. is there somewhere on here i can post it?

bạn can make it into a Youtube video then emble the exact thing in the box (ex.link) (the last number is fake so don't click on this) or...
If bạn have it on a (safe) website then bạn can put a link to it in the đường dẫn section.

(Interesting, clicking on the link brings bạn to các câu trả lời that need help as well as answered questions..., cool)

bạn can always post it as an article. That's what I would do.