Can't connect my Mac Pro4 to a Wifi I've always had an Ethernet cable to connect to, until now. There is a wireless Internet signal at my location but I think this computer may not have the hardware to connect? I don't see the antenna icon that would normally appear in the bar at the top on Wifi equipped machines. 

What do I need to purchase for this computer so it can connect to a wifi?
To see if your Mac Pro4 has a wifi device installed, go to System Preferences > Network and see if Wi-Fi appears in the list of connection types:



If you do have a wifi device installed, you can turn on its menu bar icon by clicking this checkbox: