The campaign or the game? If you’re talking about the plane campaign, press the plane icon next to the magnifying glass icon. Then, you’ll want to press “Enter” or sign up, I forgot what the button was called. You’ll atleast have to wait 1 or 2 days to get access to early access. If you do get it, press the plane icon again and press “TO BATTLE” if you want to play. For the game, go to the App Store and search “War Thunder Mobile” Then, find the game. Hope this helps!