Before you load up your world you need to change the game mode to creative. Creative mode is the only way you can fly on the console version of Minecraft. read more
For Minecraft: Xbox 360 Edition on the Xbox 360, a GameFAQs message board topic titled "How to fly in creative". read more
How to Stop Flying. The game control to stop flying depends on the version of Minecraft: For Java Edition (PC/Mac), press the SPACE key twice (quickly). For Pocket Edition (PE), you tap the Stop button twice (quickly). For PS3 and PS4, press the X button twice (quickly). For Xbox 360 and Xbox One, press the A button twice (quickly). read more