Planting a tree isn't hard. Its not difficult, a moral decision, or submission to the ruthless empire of Al Gore. Its something that's useful, pretty, and good for the planet.
Step 1: Tree sources
You don't need to go pay $50 for a tree at some ridiculous garden center. There's probably some you can get with five minutes and some understanding fellow human beings.
First, go out to your backyard. Find a tree that your cruel, heartless parent (lol) is about to pull and offer to replant it. That's what I did. Or go to a field or other generally well-tended boring grassy place and rescue a tree from there.
Remember, don't ever take a tree from somewhere it will be happy. It will be fine there. Go find one in danger.
BUT DON'T PULL IT YET.