CRO Billing is a very robust system to track all of your activity in CRO Dispatching. The two systems are separate entities, but intimately connected.
The primary way to access CRO Billing is from the "Billing" link on the CRO menu, on the left of CRO Dispatch. By clicking this link, you'll be immediately directed over to CRO Billing, where you will need to login with your CRO Dispatch credentials (since it's a separate system).
Fortunately, your CRO login will work on either side!
The one exception is if you *don't* see the Billing link on the CRO menu in Dispatching. If you don't see the link, then you won't be able to access CRO Billing or even login if you get there. If this is the case, you will need to contact your Administrator to have them give you access to CRO Billing.