Winter into very early spring is the time of year to do apple pruning. Depending on where you are, your local cooperative extension service may have workshops. My local orchard does a pruning workshop and there may be something in that area. Or check out books in your public library on fruit tree pruning. Regardless, don't try to get long-unpruned trees into shape in just one season; taking too much off at one time will cause the tree to send out a bunch of "water sprouts", fast-growing shoots which won't produce fruit and won't be shaped well as far as overall tree structure.

Best to manage these by taking out entire superfluous branches periodically rather then going over the entire tree every year like would often be done if it was young and still sizing up.

Truly, Babs' advice is sound - pruning fruit trees, especially spur-bearing fruits like apples, is an acquired skill and not something you can learn by YouTube or any other short cut. A class or hands-on training is essential.