You would program the control channels from those sites that cover your area. (Control Channels are common to all users. They are like the "traffic cops" directing users to available voice channels so they can converse. This is what is happening behind the scenes.)
The talkgroups pertain to users. So if you want to hear MSP, then program all the MSP talkgroups. (If you want to hear your local fire, then you'd program their talkgroups, and so on for other agencies). Don't forget to include the Mutual Aid talkgroups like L-Tacs. Interesting stuff there, like pursuits. When something like that happens, they patch the applicable talkgroup with an L-Tac channel, so that additional responding agencies can coordinate.
If you live in Carver County, you only need to program the Carver County site to hear MSP Metro West. The "magic" of the ARMER system is such that all of the MSP Metro West troopers can be heard on that site. So, even though Isanti County is a far piece away, you will hear Isanti county troopers on that Carver site.
Because McCleod County is in a different district (Mankato 2200), then you have to program the site you can hear from where you are.
The key to a robust system like ARMER is to program all of the talkgroups that you are interested in monitoring. Then program the fewest number of sites you can get by with. Makes things more efficient.
This system is about as complicated as it gets for a statewide system.