Issue with and confused about the redirections in Pro-Sites

Currently I have premium members site and in configuring Pro-sites on this domain ( iI have created a test site ( which requires an upgrade to view the site (makes sense, that's what i want); however, when I click to upgrade it takes me to this page ( which is an SSL page. Does this mean I have to install an SSL cert to make this work... how can I get help on making this work? I also want to integrate my WHMCS on this... please advice.