you can chose portrait or landscape in the console. this works for both mobile and desktop.
unfortunately on Ipads the game rotates, very irritating. So either you can have a screen saying "turn your device into xxx mode" when they hold their ipad in the "wrong" orientation. or you design the game to work both ways...
At least that is how I have found it working.
regarding aspect ratio and resolution the same goes as for a normal mobile game, there are tutorials for it.