Open Steam and then click on the Arma3 game Icon to start the game. When you first start it will open the Arma3 Front end. This is where you can join servers, setup mods, game parameters, and pick and save favorites, and units you join.
Next click on the “Play” button lower-left corner.
Opening Your Profile
Once you start Arma3 up look at the upper right corner and you will see your profile name.
Click on your name and it will open the profile interface, where you can change or add a new profile to Arma3.
Once you edit or create a new profile, just click OK and exit.