Im assuming your on gingerbread and installed the latest liberty 3v2.0 and want to backup your current setup before trying out custom themes (which is a great idea). Just use your Droid 2 bootstrap app to get in clockwork recovery then use your volume button to scroll down to where it says backup and restore and select it with your camera button. You'll then get more options and just select backup. It will take about 5 or so minutes to backup and once it says backup complete select reboot system. That's it! Now you have a backup.