I'm also looking to do the same, it seems there's no option to do this with the stock firmware on the NowTV Hub.
You have two options:
1) Connect your own router behind the NowTV modem/router, and have your own private WiFi/LAN using the NowTV WiFi as your guest WiFi.
2) Swap out the NOWTV router with your own modem/router.
There are positives and negatives to both solutions which you'll find in other threads.
