From the image menu click on effects and then drop shadow. Play with the settings until you have something similar to below. Walla, with all the layers on you should have something similar to below. Now you can save the image as a .psp file which will save all your layer information and not compress the image so you can work on it again later. I then was able to merge layers, move things around, and add text.
Finished products look like below.
As you can see I was able to rotate and move things where I wanted them. Working with layers can save you lots of redo time by allowing you to place separate elements on different layers. You can then move them around to get them right where you want them. If you find you are getting too many layers, you may have to merge a couple of layers to reduce the system resources you are using. One of the really fun things I use layers for is creating floral arrangements in pots and vases.