So in this game, you are supposed to hike over trees and mountains. The hiking action is very similar to the way you would do it in real life. Remember that and you will do well.
Use the hammer as if you were really climbing something and you'll see. Try to hang a hammer on an edge and pull it toward yourself. Then you should be pulled toward the place where the hammer is hanging. To jump, hit the ground (push yourself against the ground), to hang on rope you have to have the left mouse button pressed!