I bought a particle texture but the particles are just black squares. How do I fix it?

go into your inventory and hit edit on the item. from there you can choose what file you want the texture to be

The reason it's just black squares is because the particle is set to be a black square most likely. Probably that's what the previous owner of the flame particle texture had it set as. You'll have to replace it with something else of your own like Hezk said.

Also, it is possible, because this happened to me before, I had to remove the other flame particle textures from my tori folder in the game files. It doesn't update sometimes so make sure that's cleared and you redownload your character.