get a particleemitter, put it in a part, make the part transparent and have no collision, and make the part go over the area you want it to be, its kinda hard to explain.
The best way is just to play with the values in the ParticleEmitter to see what each does.
Items like the Transparency and Color can be set to change over the amount of time the particles are visible.
You don’t even have to insert the ParticleEmitter as the script on the web page suggests, you can just insert it into a Part in Studio that is the size of the floor of your room (or even into the room’s floor Part) and change the Properties in the Properties window.
You’ll learn more by experimenting than just having someone make it for you.
I’d recommend following what @Scottifly is saying. http://developer.roblox.com/ParticleEmitter | Roblox Creator Documentation as those will help you a lot especially when you don’t know how it works. If that doesn’t help try finding maybe a friend (Who knows how to do it well, and can get the job done perfectly), do research, or the best way is to find tutorials! Their are tones of tutorials that exist on the YouTube platform, but if that doesn’t work for you it is best that you experiment. Doing the same thing over and over again and expecting different results! Also the particle video doesn’t really explain anything. You should maybe try to fix that (If possible, though it may or may not be necessary), as it doesn’t really help on how it works. A brief explanation or showing how it works and how you we’re able to contradict its modifications, because from the looks of it the way it was made on the gif seems to show differences between the video and the gif its self (When I mean different I mean looks not the build or other parts surrounding it).