Fertilizer works a lot better if it is distributed around the tree, out near the drip line. Those fertilizer stakes are a hunk of fert that releases all in one place, and can burn roots near where you put them in, as well as not distributing the nutrients properly.
Advise you to take a hammer, wrap them in an old towel or something and bust them up into small pieces. Then, as Philip advised, use your digging fork, carefully make some holes and scatter the fert so that it gets down below where the grass is.
Btw the "drip line" is where the tree sheds water from its outermost leaves. Around that area and a couple of feet further out from the trunk is where most fruit trees have their main abundance of feeder roots, so don't put the fert in there near the trunk.