I'm not sure what the memory architecture of the 800 is but I assume it's similar to the 500/600. Let's say you wanted to program in the central dispatch for the county sheriff. First you would create a TSYS (trunking system) object, set its type as a P25 system and add in the system frequencies. You might be able to enter the control frequencies only like for Motorola systems, but since there aren't any P25 systems I'm interested in in my area I don't have much experience with it. Give it a name like "Polk Co. Pub. Safety", or anything else you would like. Then create a TGRP (talkgroup) object, set its DEC number to 5007 or HEX 138F, and you're all set. You can set between DEC or HEX display, which both display the same number, but in different number systems.
If that is too confusing, since you're a premium subscriber, you can just use a program to download the entire Polk County System, delete the channels you aren't interested in, and send that to your scanner.