If your tree is a James Grieve, they are better than most varieties at fending for themselves, so you might not need to feed it at all. Over-feeding an apple tree can reduce your crop by prompting the tree to make too much leaf and shoot, and not enough flower buds.
If your rootstock is MM106 (quite common) that will also make the tree good at finding food.
It all depends on your soil, I suggest you wait to feed until there are definite signs that food is needed (sparse growth, yellowing leaves).
I have two James Grieves on MM106 twelve years old have never needed feeding.