Each aircraft has a flight manual, typically very detailed.
My experience has been to refer to that manual and ALSO watch some of the online tutorials and guides. The good news is that the online community are VERY helpful and supportive. So for example, starting up an aircraft is NOT always that easy. The Mi8 helicopter requires flicking something like 60+ switches, knobs and dials in roughly the right order to get it ready for takeoff. Doing that from just the manual is not fun. Making up for that, some are frankly dead easy.
In games, there's also two types of aircraft. Most are now "full fidelity", meaning that you can actively use all of the knobs, buttons and dials that you can see in the aircraft using a mouse. There are however also 6 "Flaming Cliffs 3" aircraft. These are significantly simplified in their use and systems, whilst still retaining the core weaponry and flight models. Starting say the F15c is just 3 buttons, though learning to use the radar is a bit tougher.
If you're curious, download the basic game. It's free, includes one terrain (which is huge), it's mission editor and a couple of low fidelity aircraft. That will give you a reasonable inkling of it's complexities.
