Lots of poles set around pretending they're jumps, then once both you and your horse are calm, confident and think it's easy peasy then put it to a tiny x-rail, and go over them again and again until they're easy again, change the course up and keep at a tiny height until you're confident and thinking that it's nearly boring and you're itching to jump something bigger. Soon as you start to lose confidence or your horse gets hot, put it back down. Will take a bit. But it'll work
Take it slow. Pushing yourself after time off will only bring you back further. Work on flat some more then start at a lower level then you are used to (I had been off for a year and a half because of an injury that caused surgery). Also my horse is very excited during jumping so I circle before jumps or make him stop before and after; makes me stop and think also doesn't give him time to pick up the pace. Grids are another good thing for excited horses.
Maybe try and get in an extra stride and see if it helps I was out of jumping for a few years and got really nervous when it came back to jumping and added in an extra stride and find it really helped me with both my confidence and jumping aswell