How would i train my ranch horse dressage?

My trainer said he would be a great dressage horse with work he is 16.1 has lots of impulsion and is learning to stay on the bit and other english basics. My question is how do i train him dressage ? Nothing big just training level and level 1 later on i want to keep his mind active and he has the best extended trot and an awesome canter I would love to ride him in dressage shows instead of riding a lesson horse. I have lots of learning dressage books for myself but I have yet to find one for horses. Any tips would greatly help.