Cockpit instrumens?

Is there any place (like a website) where I can find what all the instruments are/what they mean of the cockpit of an airplane (preferably the Cessna 172 and Cessna Citation)?. Like I really need to know everysingle little knob and what they do…I’m using Flight Gear Simulator and I also need to know how to land a jet (Cessna citation), where can I find some info showing how to do that?
And also, how does a pilot know when he is already lined up with the runway how far away he is?

Try this as a start http://travel.howstuffworks.com/pilot.htm

Cessna 172 Crash