Latitude D820 - Wireless question

We just got a wireless router and have it hooked up, however, we do not know what key or switch to use on the Latitude in order to let it know we want to go wireless.  The IT specialist at work told my husband that the laptop was totally ready for wireless service, but since they don't have wifi at the office, he didn't have an opportunity to actually "turn on" wireless.  The AT&T rep who helped us install the wireless router tried several things with us on the phone but nothing brought up the wireless connection.  Anyone have suggestions?