How do I create a usb button using a teensy 2.0?

I'm completely new to using anything like arduino and teensy so I feel like I'm a bit over my head.  I need a simple momentary button to be hooked up to a desktop via usb to be able to trigger my photobooth to start.  I was doing this as a wedding gift and wasn't really thinking about how hard it would be to find/build a simple usb button.  All the guides I could find made it seem so simple that I guess I either underestimated how hard it is to do or I underestimated how dumb I am.  Either way, my friends wedding is coming up and I'm screwed if I can't figure this out in time.  

I've already bought the button itself and a teensy 2.0.  Can anyone out there please run me through a step by step procedure on how to make my usb button using my teensy 2.0 and my momentary button?

If you are desparate, hack a USB numeric keypad - like this

http://www.meritline.com/numeric-keyboard---p-37555.aspx?source=fghdac&gclid=CjwKEAjw2cOsBRD3xNbRp5eQxzYSJADZGYbzifACgGi2QiZQIaUfyXsz31Gxm0qBYvcsOXQh0k4jwRoChfvw_wcB

Neat .... and under $5 solution.

Go check out Ardino's web site. You can find examples of this easily there. Set your trigger to be a specific keyboard or mouse button and then set the arduino to emulate that button and your good to go.