I didn't really follow any specific instructions, but here's what I did:
Point the camera towards whatever you want to take pictures of. Try to use the raw mode to capture as much detail as possible.
Take as many pictures of said place as you want. I took about 30, but more images = less noise in your processed image. Since I used my phone for these, I used scrcpy to see and control the device over usb adb, mainly because I didn't want to accidentally move the device it while trying to take the next picture.
Post processing the image was done in gimp. The tif files deep sky stacker exports are usually wayyy too dark, so you'll need to adjust the brightness.
Pro tip: try to keep trees and other landscape out of the frame of the photos because deep sky stacker tracks the earth's rotation, meaning the landscape will be blurry.
Nor do I, but it’s hard to imagine you captured anything other than the largest galaxy in our local cluster with just an iPhone. That’s one hell of a shot. BTW, that thing is 2.5 million light years away.
A friend has been filling me in on his journey doing the same thing. He got to the second to last photo in a set and hit an out-of-memory error last week. He went from 32GB of RAM to 96GB. I think I'll see lots more cool images of the night sky soon. :-)