QUESTION:

How do I import a customer Excel file?

ANSWER:

You'll find instructions on the import pages: Once logged in, click on the "Manage Customer Records" on the control panel (the first page once you login) and then select either "Import Customers" or "Import Customer Transactions".

Additionally, there's an older support article with just a few more details:
http://support.stickystreet.com/forums/16257/entries/10077