Hi,

I'm a newbie to Phantom 4.

Do I use the computer to download & update firmware for the RC?

Do I use the App to update the firmware for the aircraft?

I used the app to update both the RC and the craft out of the box. Today, I updated to latest firmware again by using the app - on the RC and also on the craft. Your results may vary, but that is how I have done it, and I have had success. Out of the box the craft did get stuck at 99% updating, but I did not have that issue today.

For the drone, Download the bin file onto your micro sd card, from your computer.
The RC will be able to update over WiFi, after the drone has been updated.
You will get a prompt to update it, follow the simple instructions.

RedHotPoker

Hello, here is the updating tutorial for Phantom 4 drone :
You can update your drone via DJI GO APP or DJI Assistant 2. But as for the RC, it would be more convenient to update via the DJI GO APP.