Jonnie, Murf is pretty much spot on with what he has said. also worth mentioning that this mod is a sim so get yourself a steering wheel and pedals if your not running with one already.
gamepads tend to be pretty much full on when you hit a button, so if you imagine driving a real car and flooring the accelerator, you wont be surprised if it spins round or goes sideways. the same is said for the brakes - if you floored your brake pedal the front wheels will lock up and you wont turn into the bend, but rather slide on towards the fence.
F2's are much easier to drive in my opinion, so it may be worth starting with them and move on to the big f1's once you can handle it better?
Tosh has very kindly posted his f2 set ups a few weeks ago, so do a search for them in the rfactor f2 section of the forum. Tosh is a superstar grade driver, so you wont get much better set ups than that to be fair. Other than that its as murf says - keep doing the laps as practise makes perfect.
http://www.racelinecentral.com/RacingSetupGuide.html
Drumbstick also sent me the above link recently which explains about adjusting set ups. it is a long read, but will explain the physics side better.