Nighthawk M1 dynamic DNS support, cannot find it.

Local Telstra dealer sold us one of these for a small business office where ADSL is not feasible so the Nighthawk will be used as fixed internet access until NBN arrives in about a years time.

Client needs to use RDP to regularly connect from home to office and although we understand the Nighthawk doesn't support static IPs we were assured it supports dynamic DNS however I can't find it in any of the menus.

Am I missing something here or is there a hidden/advanced menu I need to activate to use this feature?

thanks in advance.