Hello,

Here's a basic guide to pruning fruit trees, including espalier pruning.

You can find information on fertilizing, basic plant care, fruit storage, and what diseases and insect pests to look out for here.  You may want to start with a soil test so you know what your specific fertilizing needs are.

Keeping hungry squirrels away is going to be a bit more difficult assuming you don't have a dog to help.  Since your espaliered tree is likely growing against a fence or wall, you probably won't be able to put a net fully over it and circling the trunk with some sort of metal collar also won't be effective since they can just climb up the fence.  You can try putting bags over each individual fruit, which also helps avoid insect pests like apple maggot and coddling moth.  If the squirrels really want to get in there, though, they probably still will.  You can also try a hot pepper spray if the squirrels won't leave your apples alone, but you'll have to wash your harvest extra well or it may deter you, too!

Best of luck with your tree!