To setup your Google Glass, you will be presented with 5 steps.
2) terms of service
3) Add a wifi network
4) scan QR code with Glass
You will be presented with a QR code in the setup process that you scan with your glass.
That way google glass can connect to your wifi network.
This is what the information behind the qr code looks like (it is your wifi connection data):
source and the actual setup : https://glass.google.com/setup