Assuming you understand trunking, DMA and how systems/sites and groups (and their associated quick keys) work with one another....
If I just spoke Greek, you might want to start here...
Uniden DMA FAQ - The RadioReference Wiki
Read the first 4 topics. Then go down to the bottom and download the Easier to Read manual for your scanner. The Uniden manual that comes with the scanner is better used as a coffee mug holder.
I don't know what area(s) you wish to program, but you might take the time to sit down and plan how you would like to allocate them. There are numerous spreadsheets floating around the Yahoo groups for these scanners that can help you in the planning process.
If there are any trunked systems that are listed as
Analog and APCO-25 Common Air Interface in the System Voice field of the database, the 15X will not copy the digital talkgroups (there is an option in the RR web import to prevent the software from pulling these talkgroups). Any system listed as
APCO-25 Common Air Interface Exclusive is not monitorable with the 15x. This trips up a lot of newcomers, so I thought I'd throw this out...
This ain't plug_n_play - it takes some thought to get it right. In fact you might well try several configurations before you find one you like. I know I did.
best regards...Mike