Not sure how it works by snail mail. I did all mine online. Filled out the app, and you can make an appointment for your fingerprints by following the link on the DPS site, or go here:
http://www.l1enrollment.com/" onclick="window.open(this.href);return false;
I'm not sure, but I would think that you would need to wait until you are in the system before you get your prints done.