It's accessed through the main in-game menu - during a game, press Escape and press the 'Call for Support' button that has been added to the main menu. It doesn't offer invincibility or any other kind of 'god mode' cheats and is one of the milder cheat options.
Support Call is really best for dropping in weapons and vehicles. You can also skip time and launch drones. You can also detect enemy and friendly troops, which is particularly useful for developers testing their own missions and mods. You can spawn vehicles, weapons and ammo (ArmA 3 defaults only) and these will be air-dropped to your current location. changing the weather only works for a short time), almost of all them are.
Although not all the functions will be usable (e.g. Kronzky is a Bohemia contractor and his Support Call add-on has been around for quite a while.
But if you really wants some cheats in single player, then you can add them using add-ons and mods. Ravage is designed to be difficult and using cheats will remove a lot of the fun.
