What programs do you have available? If you have Microsoft Paint 3D, you should be able to remove the black background using their magic select tool, then switch to the canvas tools and select transparent canvas on, and then save with transparency as a PNG. If you don't have Paint 3D, let me know what programs you do have and I will see how I can assist!

I use Paint Tool SAI. I saved it as a transparent PNG, you can see its transparent when I downloaded it here: https://www.furaffinity.net/view/53694982/

But when I try to use it as an icon it uploads as a black background and I don't know how to fix it :(

Hey hey glad to hear you're a SAI user! I love that program.

I have the same issues with my Monster Hunter submissions. Sadly, they all have a white background for the thumbnails and preview image, but are perfectly fine when viewed! You might need to screenshot Fur Affinity to grab the background color from it and color in the transparency to Fur Affinity's color. It stinks, but that might be the only "solution" until FA actually supports transparency properly.

Okay that's kinda cruddy, I guess I might try that though to make it the same color, that's a good idea! Thanks JavaTiger :D