Firstly your horse looks lovely and seems to have a nice jump.
Personally I think the best thing you can do is enrol in some lessons if you have never jumped before, especailly if this horse is only 4.. both of you are learning and you want to start as you mean to go on. He isnt shying away from the poles which is a good start. If for any reason you can't get lessons atm I would suggest plently of flatwork over poles (on the ground) Trotting and cantering poles. This will help you control his stride for lengthing and shortening, because when you do start jumping this will play a vital part.
Keep us posted on how yous are doing