Is there also another competing leader in the rear of the pic?? I see something that looks whiter behind the tallest main leader. If so - I'd cut that off too. I'd let all side branches on the central leader starting with that lowest one with the green & yellow leaves pointing left in the pic. Depending on how high you want your finished tree to be, you might not want to cut the central leader shorter as in Telemark's top red mark. If you want a tall tree - don't cut the leader. ( I follow the advice of Penn State's fruit tree dept. professors. I'm no fruit tree genius!!! ) They told me I want wide crotch angles on the main scaffold branches - not narrow, steep angles - so the branches don't crack when loaded with fruit. Wider crotch angles are stronger. Scaffold branches are the main side-branches that grow off the central leader.
If you want to maintain a shorter tree, Telemark's top red mark cut is perfect to stimulate more branching. ( Not picking on Telemark here!! )
There are a number of You Tube videos on pruning and training apple trees online. I bought a book from Penn State for $12 that's geared to non-commercial fruit growers. It has lots of fruit tree info on pruning, training a tree for shape, pests & diseases, nutrition, etc. Plenty of diagrams in it.