How do I change the background from a picture that I got in a attatchment I got in an email on my Samsung Rant?

So I got this picture on email on my Smasung Rant through E-mail attachments and i saved it to my files, and wanted to set it as my background...I went to change my background but couldn't find out how to do it..can anybody help?
How do I change the background from a picture that I got in a attatchment I got in an email on my Samsung Rant?
If you have the pic, just open it, take the mouse do right click on top of the picture, choose "set as desktop background"...good luck!