You need to assign the role to a group named IP_Admins

Your network contains one Active Directory domain named contoso.com. The domain contains an IP Address
Management (IPAM) server named Server1. Server1 manages several DHCP and DNS servers.
From Server Manager on Server1, you create a custom role for IPAM.
You need to assign the role to a group named IP_Admins.
What should you do?

A.
From Server Manager, create an access scope.

B.
From Server Manager, create an access policy.

C.
From Windows PowerShell, run the Set-IpamConfiguration cmdlet.

D.
From Windows PowerShell, run the Add-Member cmdlet.

Explanation:
https://technet.microsoft.com/en-us/library/dn741281(v=ws.11).aspx
https://technet.microsoft.com/en-us/library/mt210435(v=ws.11).aspx