Sorry, it's not that easy. You might as well ask for a crash course in trigonometry.
The first time I saw the radio stack in the C172 (less than a year ago) I thought it was the most complicated thing I had ever seen. It's a little bit of a learning curve but it's rewarding when the thing starts to act predictably.
First you need to learn the difference between NAVigation and COMmunication radios. The NAV radios work in conjunction with autopilot, VOR and other navigation functions and the COM radios let you talk to people on the ground - ATC, towers, etc.
FS has several built in lessons on the radio stack and this site
http://www.emeraldair.net/ (click on Training) has some good tutorials. If you have more specific questions we'll be glad to help.