Before installing a ROM you need to install the Galaxy Nexus Drivers on your PC, root your phone and install ClockworkRecovery. You can do that manually or use the GNext Toolkit. I highly recommend using the toolkit and watching the 1st or 2nd video because it explains when and how to boot your phone into fastboot mode (adb reboot-bootloader).
Once you’ve installed the drivers and rooted your phone installing a new ROM is a cinch.
There were 2 add-ons that I wanted: tethering and Facebook contacts sync. These are packaged like ROM updates but are downloaded separately (they’re linked in the XDA post for the ROM).
USB Tethering results
And the configuration screen itself. No more carrier check for tethering