You seem a bit confused, so I will try, and I say try, to help, and keep it as brief as possible.
Burlington County police departments operate on the Burlington County Trunk System. A trunk system is made up of a number of frequencies. Agencies (PDs, FDs, EMS Squads, etc) that operate on a trunk system do not use any specific frequencies. If the dispatcher wants to communicate with a police unit in the field, he keys up his radio and the control channel in the system assigns him a frequency to use, one that is not being used by anyone else in the system at that time. He then communicates on that frequency via the assigned "dispatch" talk group for that agency. When the unit in the field wants to respond he keys up his radio and the control channel chooses an open or unused frequency for him to use, and he communicates via the same talk group. The frequency may be different from the one the dispatcher used. During the course of a conversation, a number of different frequencies may be used.
In order for you to monitor Evsham PD, you need to go to the link that is provided in the post above by elk2370bruce and scroll up to "System Frequencies" and program the frequencies for Site 4 - West (Medford). You will also need to program the information from the Custom Frequency Table at the top of the page, Base Frequency, Offset Channel and Spacing. There are three listed and if you just want to monitor the West Site for Evsham Twp., I don't know if you need to program all three or just one of them. Maybe someone can clear this up. On a Uniden Scanner you would program it as Motorola Type 2 UHF System. I don't know about Radio Shack or other scanners. You will need to program Talk Group 19376 (thanks to skypilot007 for that info), in order to hear Evsham PD. Just a note about talk groups, and this applies to all scanners, if you see "DEC" and "HEX" talk groups listed, you only program the "DEC" talk groups. The "HEX" are for Motorola radios.
The system is a DIGITAL system, so, as was mentioned above, you will need a DIGITAL scanner in order to monitor it. If you don't have one, you're out of luck.
Also, if you've never progrmmed a trunk system before, my only suggestion is to read the manual for your scanner or get someone to help you.