You have a couple of options:
1) Use a prepaid tmo sim w/ data, or get an unlock code and use another SIM w/ data a data plan on it (that will require the APN for that carrier)
2) Set up adb and follow this
guide, it will let you choose an access point to connect to.
Originally Posted by psychoace
If you just proceed with the setup it will notice that you have no phone network so it will then ask on the next screen to provide a wifi spot which is where you can log onto your router.
If you've ever installed RC29 you'll know that it wont let you connect to an AP, it will only use cellular data.