Trails not working? (sorry if this is too simple)

Hi! I'm having minor problems with trials. Yes, I checked the roblox wiki (read it over a few times), the dev forum, etc, and I can't get the trail to appear.

Here's a gif of what my problem is: (sorry about my cursor)

My Problem GIF

I have a texture for the trial, but it doesn't show in studio like i think it's supposed to.

I'm sorry if this question was too simple or stupid but if you can either answer it or give me a sorce that will help me.

Thank you! ~Chez_Guy :)