Works in Photoshop 7 and later. (Windows & MAC)
After buying and unzipping the Web-Design-Shapes.csh files, place the *.csh files into:
Program Files > Adobe > Adobe Photoshop X > Presets > Custom Shapes where X is the version number for your version of Photoshop.
Find the folder where you installed Photoshop (usually your applications folder), and choose Photoshop > Presets > Custom Shapes.