Below are some improtant videos all ArmA players should watch at least once to get a full understanding of ArmA 3.
BASIC ARMA 3 VIDEO GUIDES
STEP 1: INTRO INTO ARMA 3
STEP 2: Terminal Ballistics - Game Mechanics
STEP 3: Basic Infantry Tips
STEP 4: Movement & Shooting Overview
STEP 5: Basic Multiplayer Tips