Could someone teach me to play ARMA

[Mahti]

You can't really learn playing DayZ but rather play teaching missions, In youtube for example there is easy way to learn how to use PSO sight for example or other scopes, Its handy to know approximately how far your enemy is so you can shoot target without wasting bullets also if you like real realism I suggest to go for A.C.E it includes many features like fueling in air or proper radar systems.
Myself I have played a lot of Arma and around 1000 hours Arma 2 I got around 50 Gbs addons installed which includes New radio system, Realism overhaul, Tons of new vehicles weapons etc including Finnish defence forces for example.