WHMCS is already setup to support the PayJunction Payment Gateway. If you do not see the PayJunction gateway listed in your WHMCS Admin section, please contact the WHMCS support department by submitting a ticket. They will then provide you with the PayJunction payment module.
You will need to be prepared with your PayJunction QuickLink API login and password:
QuickLink API Login and Password
To see how to set your QuickLink API login and password, click this link:
Then, plug your QuickLink credentials into WHMCS when requested.