The first thing I will mention is. Programming a scanner like that will be much easier with the correct software. If you get a RR subscription you can even down load th info right into the scanner itself.
Here is a list of software that will work for you scanner, See All Object Oriented Scanners
Object Oriented Scanner Software - The RadioReference Wiki
Going on the assumption you want to listen to McHenry County, IL you will want to program the Starcom21 system into the scanner. This is a P25 trunking system, on a trunking system no specific agency is assigned to a particular frequency. The users float between the frequencies as they are available.
Here is a great video to describe how trunking works
https://www.youtube.com/watch?v=J_SvqbP7kjw
If you are going to program the scanner manually I would check out this manual
Easier to Read Pro-651/652/106/197 - WS1040/1065 - PSR 500/600 Digital Scanner Manual
McHenry County uses StarCom for most of it's communications, you will want to reference the following page for programming.
STARCOM21 Statewide Illinois Trunking System, Statewide, Multi-State - Scanner Frequencies
You will want to add two sites to your scanner, do not add all the sites in the system because they will not be in range of you scanner and you will slow down your scanner.
1-20 McHenry/ISP - Simulcast
1-46 McHenry County - Simulcast
Once you add these sites to your scanner you will want to add the following Talkgroups that you want to hear.
McHenry County Talkgroups, ISP Talkgroups,
** It does appear that a majority of the McHenry Talkgroups are Encrypted, this means that you will not be able to hear them.