Regardless, are you working with an instructor or attempting to self teach? Hopefully it's the former. It's very easy to develop bad habits quickly and you need a pair of eyes on the ground to coach you. If you have been doing good flat work for the past 5 years, jumping should be a mere formality since flat work is the most important part.
Ride the course as if it were on the flat. Jumping, regardless of hunters or jumpers, is a way to test you and your horse's training. Throughout a course, you will change leads, shorten and extend strides, count distances, correct balance issues (especially in jumpers), and keep a good, and controlled, gait. There are 12 fences in some courses. The rest of the time, you are on the flat. You need to perfect your flatwork before worrying about jumping. Every loophole you took around the flat work schooling will be evident when you are jumping, since you need to be in constant control and ready to change something at any moment. You have to be aware of everything around you- your horse, the next jump, how you should land after the first jump to get to the next, what lead this jump will take.
Also, don't over-think the jumps. So many people, including myself, like to jump ahead of the horse's movement. When I tried correcting that, then I would get left behind. Don't think ahead and don't try to under-think it either. It's a jump. Shift onto your thighs and release. The horse's movement is what opens and closes your hips. That big two-point you see Grand Prix riders doing? It's just a shift onto the thighs and a big release. The horse is what puts you into the position the rest of the way.
Good luck! Jumping is a great way to test yourself and your horse. And, it's such good fun too!