If you're in the US, that's the link. However, this page (www.csj.org.uk/anglo-assocs.htm) will show you how to get in touch with other national groups if Jen lives in another country. A backup is to pick one up at the first albergue or pilgrim's office along the route. Sometimes, tourist offices and larger churches have them as well.
It depends where you're starting from, Jen. In St. Jean you can get it at the pilgrim's office for 2 euro. There's a FAQ's link at the top of this page where you get almost all of your questions answered, and you can use this link for more (it also links back to some great resources here). http://www.theroadtosantiago.com/
Your profile says "...leaving Colorado..." Am I correct to assume that you're in Colorado? If so, contact the American Pilgrims group that Falcon mentioned. They will issue a credential to you. If you're in the Denver area, the local chapter of the American Pilgrims is having a shell ceremony on March 22. This is an impressive ceremony held a local church, where they present prospective pilgrims who will be doing the Camino during the current year with a scallop shell, and then a meet and greet social afterwards at a nearby tapas bar. Check the link for the local chapter which is found on the main American Pilgrims website for more info on this and their mentoring program for prospective pilgrims.
If you're in Denver or anywhere along the Front Range, contact the local chapter and give them your name so they'll have a shell for you at the shell ceremony -- assuming you can attend. The journey becomes very real when you have your credential and shell in hand, even though your departure may be weeks or months away.
Go to www.americanpilgrims.com; you'll see an orange-colored menu under the main title, click on Local Chapers, then Colorado Front Range. You'll see the shell ceremony under "Scheduled Events." We may see you there, depending on some other travel plans that are in the works.
Jen...hitting that button was the same for me...that it was finally REAL! Enjoy and Buen camino. My husband and I walked from Valença to Santiago starting last June. Ahhhh.... I dream of walking lately and have decided I will have to go back. Don't know when... but will go back!