You just need to setup internet sharing from your computer, since that looks like a usb 3G type internet device. Depending on your OS, many different ways to do it. windows would be the simplest. just follow the wizard.
Pretty sure if he is plugging modem into his machine directly he will need another radio (or use the ethernet and connect his ant wired).
Simplest thing would be to get something like this (
http://www.amazon.com/EW-7811UN-IEEE-802-11n-draft-USB/dp/B005CLMJLU)
and then setup internet connection sharing in whatever OS you are using.
Last i checked you can't plug usb into an ant. unless someone made an adapter for that control board? Easiest thing is to do ICS in windows.
Not suggesting you plug usb into ant. I am suggesting that the 3G radio is plugged into his desktop/laptop and you will need something with an 802.11 radio in that same machine to act as the access point piece. Or plug his ant into the ethernet port on that same machine and set the sharing up that way.
To have a gateway you will always need two interfaces (ethernet, wifi, wimax, 3g usb modem, etc)