I made a detailed list of steps on how to make your own galaxy but my computer had an error and it was lost.
Here it is in a simpler version:
1) Make a star 50xsun with velocity 0.00 meters/second.
2) Pause game and turn time step to less than a second.
3) Apply multiple types of rings.
4) Unpause just enough to rings smear together.
5) Pause and click orbit all button.
6) Watch as matter condenses and forms lines that slant inward to create arms.
7) If you want to slightly decrease the mass of the star.
8 ) Adjust these statistics until you get something you want.
Since my picture won't work please post pictures of your galaxies. Try to change the way you make it compared to what I did so they all look different. Maybe shoot objects to change the shape of it.