If you are unable to continue to the Pay Now step of the wizard, then this means you are not using a secure form.

1. Check the URL being used starts with"httpS://"(Note the "S" part). It has been the case with some organisations that when they've added the form to their website, they have missed this part.
2. That the URL being used has ".secure.force.com" in it. Eg."https://xxxxxx.secure.force.com/"For more on this, check the setup procedure How to connect your new site to your Merchant Facility
3. Make sure the Secure URL (points 1 and 2) is entered on the Merchant Facility "Site URL" field