If you have not installed wireless firmware to support your wireless network card during Debian wheezy installation you can do so later by enabling debian's non-free repository. Here is how you do it. First open your /etc/apt/sources.list file and change line ( your repository mirror may be different ):
deb http://http.debian.net/debian/ wheezy main
deb http://http.debian.net/debian/ wheezy main non-free
Once done update packages list with a command:
# apt-get update
After the above command you can install firmware-iwlwifi with command:
# apt-get install firmware-iwlwifi
and you are done. Then may wont to simply use modprobe to load iwlwifi module or reboot.