You must first place another image from Image > Place or drag from another document, then click on layer with image (layer with image which you want behind) on LAYERS palette and drag it below layer with image to be above.

is to place image on it

is to place image on it

Click PLACE. The window will open (Like a load picture window) select the image and click "Load". The image appears on the topmost layer ready to be moved

Muslims Symbol's website is one place where an image of the Muslim symbol can be found. Photobucket's website is another place where one can find an image of the Muslim symbol.