In Salesforce there is a C&P Importer, what can be imported using this application?

I have an event that participants are registering through my web site - everything is going great, but we have some participants signing up through someone else, would like to upload these participants through Click and Pledge so they can be signed in at registration, add them to my contact lists, and make them members - can I use the C&P Importer to accomplish this task or do I need to hand key in each outside participant through the Box Office application?