Theslam3

Hi i need some help. I have been playing arma 3 for years and i have 1700 hours on the game. i have never been able to zero in my gun scopes and vehicals, this really sucks because i cant sniper that well and using vehicals is very hard to hit stuff. i have tried changing the keys in my settings and have tried new keybords. can't find the pronlem PLEASE HELP!!! Thanks Michael