Go to Google search bar and type in:
Youtube pruning apple trees

All the videos on the first page are great...start with the ones by Stephen Hayes. He's in the UK and does great videos. Start with those and watch a few more. You'll have all the knowledge you'll need.
Yes, it's that simple. BTW...a 3 y.o. tree no matter how neglected will be a snap to straighten up...should take about 10-15 min. including clean up, but if you're like me you'll take at least a half hour because you'll think you need to carefully think out every move.