Greenbottle3 said:
< downloaded the Minecraft snapshot. But < doesn't know what to do from there.
Assuming you have Windows, you can type
%appdata% in the "run" dialog window for an easy shortcut to your Minecraft folder. (It's named ".minecraft", so it should be easy to find) After opening the .minecraft folder, you should open the "bin" folder.
In there, there should be a "minecraft.jar" file. You want to preserve this file, for when you're done with the snapshot and want to return to 1.3.2 (just put it on your desktop or something). After doing this, grab your snapshot file (should still be as a .jar package) and put it in the "bin" folder, where the original minecraft.jar file used to be.
That's it!
EDIT: After you're done and want to return to the previous Minecraft version, remove the snapshot "minecraft.jar" file and put the backed-up minecraft.jar back.