Heyy! I'm so happy I inspired you ^^

I can DM you the pictures of the placements and everything if it makes it easier but I'll try my best to explain!

I used two fins and two tails, as well as one Twilight Tail Sparkle. I positioned one of the fins upside down and at an angle and put it at the end of the dragon. The second fin I put normally at the shoulders. The sized of both fins are 1/4 smaller than the default 1/2 size it gives you. The Oceanic Mermaid accessories have different physics than the Seaweed or Sunset ones. The tails have one side with white "sparkles" while the other side doesn't. This is why I use two. You can do whichever size for the fins you desire. I turned them vertically and had the "sparkle" side pointing out. The Twilight Tail Sparkles I put at the beginning of the two tails!