To register and lend on Kiva Zip, a user clicks the "Zip" tab on kiva.org and logs in to their Kiva Zip account by clicking "Register" and filling out the registration form. They can then search for and select a borrower to lend to by clicking "Lend Now", selecting a loan amount, and completing the checkout process using PayPal or a debit/credit card. Once payment is processed, the user's name will be displayed as a lender on their profile and loan pages.