The multiplayer is local only, so that means that you need to connect both devices to same network.
Then start a world on the one of devices, then it will be showed on the other devices multiplayer menu.
Then just connect to the server and boom.
I hope it helped.
(Idk if it will work on same itune account)
it should work, my ipad and my daughters ipad are on the same itunes account, we sad next to eachother and played minecraft over our wifi.. when its searching for a world to connect to i noticed it said 'stevie' rather than the name of the world, so i dont know whats up with that, is that the chars name? maybe just try connecting to whatever shows up on your list if there is anyhting at all.