This is a great exercise that challenges your grip and single arm strength as well as the connection it has to your core. You will need to be fully engaged from your center (core = spine, hips, glutes, abdominals, etc. working together), all the way to your grip strength. The stronger the connection, the stronger your posture and the stronger you will become.
This takes practice and is not an exercise to rush through. Take your time with the setup and getting the KB into the shoulder press position...this is step 1. Work with each attempted rep and try to perfect the press through its full range of motion. You must be able to lock the arm out full at the top and pause. Then slowly lower it to the starting position.
Begin with 3 sets of 3-6 reps for each side, with a light to moderate weight. Again, practicing the movement is key.