Hi, I just bought a french horn and I'm totally new to the instrument. There appears to be the whole assembled french horn (single), but it also has a separate loop + u-bend piece. It's like a ring circumscribed around what looks like the end of a trombone slide. I'd link to a picture but since I'm new to the forum they won't let me. Do you know what I'm trying to describe? If so, what is this and what do I do with it? Thank you!

If this is a single F horn the extra tubing (called a 'crook') is possibly an Eb extension which transposes the complete instrument from the pitch of F to Eb...it's difficult to be sure as you can't download a picture. Your best course of action is to contact either the manufacturer or the retailer and they will describe exactly what it is you have.
Good luck with your studies on 'the best instrument in the universe'

Thank you so much for the reply. I'm really excited about learning 'the best instrument in the universe'! It's been my favorite instrument in the orchestra since I was very little.

I looked up pictures of Eb extensions and I think that's exactly what it is. Thanks again!