How to turn roaming on using a AT&T Netgear 770S Hotspot

Netgear AirCard 770S, Firmware Version- SW19X15C_01.03.06.52  I'm using this Hotspot on a Windows 7 PC and use Boom Mobile as my ISP and the Blue AT&T Plan. Roaming is off on my Hotspot Boom Mobile told me to turn on Roaming because it is Free with my account with them. I can't find out how to turn on Roaming. Boom Mobile told me to get in contact with the company that made the Hotspot. Can anyone here help me turn Roaming on in my Netgear AirCard 770S Hotspot. I'm tech dumb and would need step by step help to do it.    Thank you  jas_hop