"I didn't do it to mess with you, I said it was to cool that oh so hot head of yours, it being funny is just a pleasant side effect, you should really learn to listen." I said, smirking. I prepared for an attack from the girl. I wasn't a complete novice with my magic now, I could erect a barrier that could hopefully take the brunt of her attack... I slipped my hand into my pocket and felt the brass knuckles hidden within... I was away from my bow, my other weapon would be a bit too deadly, I'd have to rely on my hand to hand skills and magic if it really came down to an altercation...
You just introduce your character in any way that you see fit, really. Just arriving at the school if he's new and just arriving, or just awakening in his dorm if he's already there would be good places to start with your post if you're stuck.
"Oh absolutely hilarious." I said keeping the same cheeky grin, doing my best to not show that the volume of her voice was unnerving me. I crossed my arms and smirked. "But of course, it was to serve another purpose, I think you needed to cool down. But, it looks like I didn't have enough water though, pity I didn't have a whole bucket. And I think I would love having some water poured on me just about now, I mean you're so full of hot air after all, it's simply sweltering over here." I said, fanning myself with one hand and taking a few steps back.
I felt the temperature rising and sighed softly. I quickly identified the source of this sudden rise in heat. I reached into my suitcase and pulled out a bottle of water that was half empty and screwed off the cap. I walked up right behind the girl who was causing the temperature to rise and turned the bottle over above her head and watched the water cascade down. I waited for the bottle to be completely empty and shook it a few times to be sure. "...There, have you cooled down now?" I asked, grinning cheekily. If this doesn't put me in a lot of people's shit list, then nothing will... right?