The Recurring Billing interface is designed for variables to be passed to the Gateway in the background via an "https" call through a script, processed at SecurePay.Com and then sending a response to the request object with a the return variable set. In addition the transaction will be added into the Securepay.Com recurring billing transaction database and set up for recurring billing based on the variables passed.
Below is one example of a payment form that you can use for your site: