I know how to ride horses. I can go all the way up to galloping but I can't jump. When should I start jumping?

I have been riding over 15 years, and I still have not learned to jump. xD

You may start jumping whenever you feel comfortable.

Start by walking, trotting, then cantering over ground poles. Raise them little by little when you feel confident and comfortable enough. For your first "jump" (low), I suggest getting off the horse and running with the horse over the jump a few times. Mount up and make the horse walk over the jump, then trot. When you get up to the canter, stay straight in the center of the jump, lean slightly forward, stand up in the stirrups, and hang on! The horse should naturally jump over. Congratulations! You've done your first jump! :D