The CMS does NOT directly integrate with or interface with your CCBill account.
Included within your cms templates within
PHP Templates:
/cms_admin/phptemplates/[templatefolder]/join.tpl
Smarty Templates:
/cms_admin/smarty/[templatefolder]/join.tpl
Within this template you'll put the code CCBill gives you for the payment button. Take a look at the join pages of some sites and get ideas. CCBill will install their script and should be able to give you more info on the join forms and such.
