Start with the database here on RR.Com. If you are unsure of the terms being used, I recommend you go to the Wiki and read up on "Trunking" so that you have a framework for the data.
Then, make a list of all the stuff you want to program. There are some worksheets on Uniden's web site (
http://www.uniden.com/products/index.cfm?cat=scanners) that can help you organize the information for the scanner.
Finally, press MENU, select Program Systems, select New System and follow the menu from there.
You might also find that someone else has already programmed what you need. If so, get their "UASD" file and use the Uniden software to simply transfer their setup into your scanner.