Depending on how the vendor and practice find it best to manage Direct addresses, either the vendor can manage the creation & deletion of Direct addresses for the practice or the vendor can provide the practice the ability to manage the creation & deletion of Direct addresses themselves. If you are part of a practice please contact your vendor for their preferred way to administer the accounts.
If the vendor chooses to manage the Direct addresses for a practice, the vendor can use their domain administrator account to create the Direct addresses. In the case the vendor chooses to provide the practice the ability to manage their own Direct addresses, the vendor using their domain administrator account will create a facility administrator for the practice. Providing the practice with the facility administrator credentials will enable the practice to manage their own Direct addresses.
Please note the decision to manage Direct addresses on behalf of the practice is not a choice the vendor needs to make consistently across all of its customers. The vendor can choose to manage the Direct addresses for some of its customers and allow its other customers to manage their own Direct addresses.
The way in which Direct addresses and facility administrators are managed depends on your vendor, Nitor Group provides the HISPDirect REST API and an administrative portal for managing your Direct addresses and for your vendor to manage your facility administrator account. A tutorial for the administrative portal's use is available here. However some vendors have chosen to use their own product to manage accounts in which case you will need to use your vendors solution.
In the case where your vendor has chosen to use their own product to manage accounts, much if not all of this information here will be irrelevant as their product may hide all this detail from the practice so as to simplify the practices workflow.