Look to the way you want to go when you land, open the rein to the side that you want your horse to land on and keep your body balanced
Make sure your horse is balanced, an unbalanced horse is unable to change its lead. Look in the direction you want to go (left/right depending on which lead you want for the turn) and use a slight open rein while in the air.
Put your outside leg back and open your inside hand and look to the inside 👌🏻
Your horse needs to stay in balance already before the fence. Keep your outside leg a little bit stronger and back in order to keep him on the correct canter lead also after. Your horse needs to be around your inside leg already before the jump. If you are in balance before you will in balance after :)
Hope it helped !
Keep him/her straight after the fence. Use your out side leg to help it out. Hope that works.