In order to use the Passbook you must add a pass; otherwise, you'll only see a generic welcome screen.
Using your device, navigate to http://www.passsource.com, a site that was created by Kudit to help generate passes.
Tap to select a pass you would like to generate.
Input the details required for the pass. Note: Some pass types will let you fully customize the pass with everything from location to barcode to color.
Press the Create button once you've entered all the pass information.
The pass will then be opened in Passbook. Press the Add button at the top right to add the pass to your Passbook.
You can now open Passbook from the Springboard to view your passes.