Hi and welcome to the forum..I do agree with everyone who has suggested getting a trainer to help you, it really is the best bet..You'll have MUCH better luck at being successful when you're working with a trainer. I would also take a look at a thread I started, Barrel Racing Exercises and Drills.
, it has a ton of good information and drills for a beginner and most drills are even done with finished horses. You just have to realize that training a horse for barrels is NOT a fast task. It takes years to start, train, and season a finished barrel horse. If you push your horse too fast you could sour him or worse...That said, just keep things fun and different when working barrels with your horse. Don't make every ride about "work", if you both are new to this you'll both learn a lot along the process..Probably both good and bad experiences, so don't get discouraged if things don't go as planned or take longer than you'd like. It's better to take your time and have a better (and longer lasting) horse in the long run, than to rush your horse and sour him on the pattern..You'll both be miserable.. A trainer can give you much better advice because they are there in person and can address your needs as well as your horse's needs. Anyway, good luck and remember to take your time! Keep it positive and fun..It will come with dedication, hard work, and time..