The A-10C is the original high fidelity beast for DCS World. It brought about clickable cockpit fixed wing flying and a level of complexity not seen before. It’s got a few nicknames, but everyone knows about the distinctive BBRRRRRRRRRRT!
The Grim Reapers have, yet again, created a fantastic tutorials playlist for the A-10C and it one of the first stops that I would recommend to get an understanding of the systems in the A-10C.
For those of you that prefer to learn in a hurry with some explicit content Crash Laobi has a one-minute DCS playlist for the A-10C too
Ralfi has also created some tutorials for the A-10C, quite some time ago, but equally valid: