Thanks again for all your kind comments.
If you want your paper clips to appear "attached", place it behind or above the layer you want it attached to (depending on the look you want).
Select your eraser tool (on the left), and on the top of the screen I chose block, to get a square eraser. Now erase the part of the image would not be shown if it were actually attached. I did it both ways for you to see in this layout.
Remember, you can always select Edit>undo, or if it really goes badly, throw away the layer, and drag the clip back in and start over.