Apple is a wonderful wood for smoking, especially with pork.
I would recommend that you let it "season" before using, which is just letting it naturally dry. You can cut it into chunks at any time, and you may find it easier to cut while it is green. Then, let it dry for at least three months, or if you have the patience, more like six months. If you cut it while green, it will season faster.
Wherever one lives, trees need pruning, and occasionally, you have to cut one down. I get a lot of my oak wood chunks from pruning my own Oak tree, or from asking a tree service working nearby for some of their branches. Free wood!
Seriously, when I see a crew pruning an oak tree near me, I ask them if I can have some wood for my smoker, and they cut up pieces I can carry home, or stuff into my Mini Cooper. In other words, you can get some good wood for smoking by scavenging for it.