Hi everybody, first post here. I started using Unity recently and purchased "Unity Game Development Essentials" which got me from no knowledge in coding to a decent amount in two days. After completing the book, I wanted to start my own simple project, a simple 2D game, the kind where you have to balance a motorbike or some other vehicle up jumps (you know the kind). I immediatly opened up paint.net, hoping that I'd be able to import images into the game world and then give them colliders. I could get them in my assets but not actually into the scene itself. Is it possible to do this? And also, If I can't and I need to make them in an alternate program, which one would be best? (Would wings 3d work?)
Thanks in advance and I'm looking forward to posting here in the future, hopefully I might even be able to help someone else one day.
 Basically, I want the character to be able to roll up and down these hills. I was hoping I could just add the picture to unity and then add colliders to it and then ake a skateboard which would then be able to roll along with it. What's the easiest way to do this because I don't think that you can do this with .png.