Credits: mno

How to get a helicopter
Apache is selling by Wandering Trader called Bronson - you may want to look for him in a desert. The helicopter is not a cheap toy to play with, you will need to pay 20 emerald blocks for it, and four more for each minigun.
After you've bought a helicopter, you'll first need to fuel it using Nether Ingots - it may take a few of them. Just feed them to him.
Now you probably want to arm your Apache. You can load four miniguns on the chopper, but it's a bit tricky. First, you need to hop on the helicopter to switch it into a carry on mode. The next step is to get off Apache take a minigun, to point somewhere the edge of the wheel, and tap it. It may take a few tries to do this right. I've showcased it in the video, you can watch it to see how it's done.

Video:
How to install addons:
- Download addon into your device
- Find and open .mcpack or .mcworld files that you download earlier
- Click on it to import into Minecraft Pocket Edition
- Open the game
- Create new or edit an existing world
- Scroll down to Add-ons section and select the ones you want to apply
- Make sure to enable "Experimental Gameplay"