This is the marquee tool which basically selects a part of an image in the shape of a oval you can also do it in a square shape.

 After i selected a part of the image I feathered the image. I did this because it blends the image so that it dosn't look like iv cut and pasted it.

 after the image has been  feathered

 then i inversed the image because i didnt want to edit the inside of the circle.

i selected blur then radical blur