Hmmmmm, if you've never trotted before, on any horse,,I'd strongly suggest getting at least a friend to help you experience it the first time. Most instructors will have a novice (even if just novice at the trot!) ask for the trot the first time while on a line. So, someone is holding the horse on an at least a 22 foot line. Have a halter and a bridle on the horse, but the bridle is more of a safety net with the line snapped onto the halter. This way you don't have to try to think about steering along with the new sensation of going faster and possibly bouncing quite a bit. (dont know how smooth, or rough your horses trot will be !) It will help your confidence as well as probably keeping the horse calmer, in case he gets 'up' a bit when he increases his gait,,and/or feeds off of your emotions (if you feel a bit unconfident).
good luck! stay safe. have fun.