Thank you for comment. I added description on how to play game so people won't get stuck at first scene and get confused about chopping trees.
So yeah you need to go straight up and follow path where you'll find ruin that will give you more info. You can open map with M and select forest. There you can chop trees and plant them. They grow back in 30 seconds if you plant them. They will also grow if you're not in forest scene.