The one-click panels that run the Greeting Card Designer for Adobe Photoshop are only supported in Photoshop CS4
If you have CS4, the panels should have been installed when you installed the Greeting Card Designer actions.
To find the panels, open Photoshop CS4 and go to Window > Extensions...
You should find two extension panels, Create Cards and Modify Cards. Simply click on each one to open the panel in CS4.
If you do not see them there, you may need to restart Photoshop. In extreme cases, you may need to reboot your system. Extension panels are something new to Photoshop and don't seem to behave consistently from one system to another.
NOTE: Panels must be "registered" by Photoshop in order to work. The first time you try to open them you will get a message to restart Photoshop. Once you restart Photoshop you should be able to see and use the panels. Look in Photoshop Help to learn how to manage panels.