WRITTEN TUTORIAL FOLLOWING: SCROLL DOWN FOR ELEMENTS INSTRUCTIONS
If you are using Photoshop 7 or a newer version:
My understanding is that these shapes load in pretty much the same manner, whether you are using photoshop 7 or CS5. I have heard it is possible to extract files directly into Photoshop, but I haven't done this myself, so I am afraid I can't offer much insight on HOW to do it. :) The files come in a Zip file format, so you will need a zip extractor program to un-zip them. If possible try to keep track of where your files will be extracting to, so you will be able to locate them again.
After the files are extracted open photoshop and click the custom shapes button. There will be an arrow next to the selected shape on the toolbar. Click that arrow, and you will see a preview (displayed as thumbnails) of your the custom shapes that came pre-installed with photoshop. You should also see a double arrow on the top right corner of this menu. Click that and scroll down to "load shapes." Browse and locate your extracted shapes, click on the shape you would like to load. It will instantly appear and will be ready for use! P.S. You may or may not have to load each file individually. I think this depends on what version of photoshop you are using. :) For visual instructions click this link HERE.
If you are using Photoshop Elements 7 or higher:
Because Elements does not allow you to access your custom shapes with the preset manager, I had to devise another way of loading my custom shapes. What I found to work was to actually create a shortcut to Elements on your desktop. You can do this by finding the program located under your start menu, then right clicking and scrolling down to "sending to" select "desktop" from the fly out menu. If you are using vista I think it may actually say "create a shortcut" after right clicking the program.
After you have the Elements icon located on your desktop you will need to make sure you have your shapes extracted and saved to your desktop. After doing that... you will need to open your folder containing your custom shapes. Drag and drop all the .csh files into Elements. Clicking your custom shapes tool will open your shapes, where your new ones should be visible and ready for play! If these instructions do not work for you, you can check out this tutorial I found for loading shapes into Photoshop Elements.
I think that about covers it all! Don't be afraid to get creative with your overlays! I look forward to seeing what you cook up. :) Of course if you have any other questions feel free to ask away!