Prune when you have time. Thin in winter, head back in summer. Have a plan (design) for the tree, follow it. Apple trees can be trained in various styles. Unless it was a small, unbranched whip your specimen came already partially trained to a particular style, you paid for this preparatory work as part of your purchase price. You might like to identify what training method was used and continue it. Look for drawings showing training and pruning of apple trees on web sites and in pruning books. A good one with illustrations of various training styles is (RHS) AHS Pruning & Training .
Misty Dog... Do you have an online album you can put a digital photo on to link to from here? I prefer one variety per tree so I can start a central leader and train the trees into tall narrow pyramidal forms. Mine are about 14' tall and only about 3' wide at the bottom. Very tall and narrow. Much better than espallier for my use.
