well there are 2 external antenna jacks. if I remember right the one by the power button is the cell radio, and the other is the bluetooth wifi. but i'm not positive. regardless you need to make contact with the center pin.
otherwise pop it apart and tape some foil to where the stickers were connected. (there's a spring that pushes against the sticker)
pics here
http://forum.ppcgeeks.com/showthread.php?t=49932