How to create a clipping mask in Adobe Illustrator.

First create an circle, really any shape will work.

Next find the back ground image you want to use. Have both objects on the same layer.

Next move the object over the back ground. Select both items using your rectangular marque tool.

It’s the one that looks like a square drawn with dotted lines.

Right click some where on either object and select Make Clipping Mask.

When your finished you will have clipped out the back ground in the shape of your circle.