First start off by creating a world, make sure when you create the new world that you disable [Online], You can use can switch this after you have modded your game save. After creating the world try and fill each one of your inventory slots [The ones at the bottom of the screen] It doesn't matter too much about the other slots but the more slots the more items you can mod. After filling your inventory the best you can save your game and move it from your Xbox to you PC using horizon like so.


Once you have extracted your save game open up 360 Revolution and navigate to the Minecraft save editor and open your save, it should look something like this.



Now you can edit your inventory with whatever items you like, please note that you should refrain from using items that are not in game yet [The save editor has some items that have not been implemented yet and they will crash your Xbox if you try to load them] Also do not try to stack non stackable items e.g. Having a stack of 64 Diamond Pickaxes, you must only have one per slot. Once your done it should look something like this, don't forget to save before exiting.


Now drag your save back into Horizon and Rehash and Resign it, then save back to your device. Once you have your save back on your Xbox make sure when you load your game you disable Online again. Let it load and enjoy your new modded items. After this if you wish to play Online it is safe to do so.