Azure Site Recovery uses two types of credentials, one for connecting to vCenter to discover virtual machines and the other for installing the Mobility Service into the virtual machines or physical servers you want to protect.
At the point of installation, you enter the credentials for both vCenter and the Mobility Service. The question is how do you enter more credentials in the future?
The answer is to browse to your installation location E:Program Files (x86)Microsoft Azure Site Recoveryhomesvsystemsbin and launch cspconfigtool
This gives us the ability to add extra credentials
Azure Site Recovery is a work in progress and Microsoft have introduced some significant updates in the new version. I would advise locating the cspconfigtool on your Windows desktop for future reference.