ProSite, WHMCS Provisioning, Stripe and SSL

I need some professional advice before I even start with this. How should I setup SSL? I have:
- Cpanel with multisite installation
- CPanel with WHMCS with WHMCS Provisioning
- Both of the above on the same Dedicated IP

I only need SSL on multisite for credit card charging purposes (Stripe, ProSite), and only for the checkout page on multisite. And for WHMCS, well I am not sure, but I think for whole WHMCS.