Its pretty easy to get to work. I can show you some screenshots.
Warning! Don't play on any world that wasn't created on the snapshot you're running. It would probably workout just fine but, you have a chance of losing the world data. Also, if you make a world in a snapshot DO NOT OPEN IT in an earlier version.
Open the Minecraft launcher
Click on the button that says "Launch options"
Click on "Enable snapshots"
Click back to "News"
Click on the arrow next to the "Play" button
Click on "Latest snapshot"
And then you should be able to play on snapshots!