There are four wires in a usb cable.
How do you connect them to a Sparkfun Explorer Regulated Board?
Red and Black are obviously 5V and Ground
But Green and White which is Data plus and Data minus, where do those two go?
It looks like that board is only for level shifting between 5V/3.3V serial signals. The board itself doesn’t have a USB to serial converter so you can’t hook a USB cable directly to it.
You either need a USB to serial converter which you can then wire up to your board, or just go ahead and get another board with built in USB support, like the XBee Explorer USB.