You have many hobbies, presumably. Horseback riding is your favourite, but you could make it about a couple of them if you wanted. Or you could talk about your favourite horse.
Just remember that whatever you talk about, your classmates aren't going to care and will find it boring. That's the nature of stupid orals in school.
There's no need to introduce yourself. You're talking to your class, they know who you are. I know this is a presentation, not a debate, but there are loads of weak, ineffective or clichéd ways of opening your speech that debaters are drilled into avoiding.
One way you could open is just to walk up to the front of the class, grin, and say, "Hey, everyone. I'm going to tell you a bit about some of my favourite hobbies. I play the clarinet, I teach Burundi children how to read, I'm sous-chef for a four-star restaurant and I recently submitted designs for a new circular supercollider to CERN, but the best way for me to pass the time has to be in the company of my horse, Sonny. Everything else is great, and cool, but Sonny just rocks my socks off."
If you believe everything you read, better not read.