not square Barriers and Walls

Hello, i watch a lot of tutorials, but didn't find how to do for example circle form barriers. I need to do circle form springboard, first of all i try to paste .png image with transparent background but it doesn't work..
p.s. sorry for my terrible english
p.s. sorry for my terrible english

Comments
In there you will see Collision shape Rectangle or circle.
Your image will still be a square but the collision area is now a circle