If you can get a signal, you'll see an SSID of "Virginia Tech". Connect to this and it'll ask you to sign up with your email and phone number. It'll then text message you a password and you can login. It's only good for for 8 hours (might be 6, can't remember).

That said, we're in Lot 8 (Litton Reaves) and we tailgate right up against Wallace Hall so signal is no problem. Last year, because of the water main break, we had to move to the far end of that kiddie playground and the signal there was pretty much unusable. So it really depends on how close you are to a building.