Replace the external power button

My button fell off and got lost. I just bought a new one in a kit from Amazon, but I have no idea how to replace it. There are no instructions in the package, just the power button and the volume button. Bing and Google searches are no help because these numbnuts confuse the button with the switch inside, so they post videos about replacing the button when they mean the switch.

I would appreciate help from anyone who knows how to replace the power button.