Please see the link in my sig on how to use the screensaver hack. I'm going to assume that you have the K2 International. Just make sure you use the correct .bin file for you Kindle. If you pick the wrong one it won't hurt your Kindle it just won't work (the option to update will be grayed out).
It's a very simple hack. Also make sure your Kindle is already updated to the 2.3 firmware
. (home >> menu >> settings >>> look at the bottom of the screen for the version number.