Using MEL
 

Hi al how can i use mel?
I donloaded some mel textures how can i use them?

are they *.ma files, or actually mel, you can open the script editor (very bottom right) and then go file open script and find the file, then hit enter once its loaded

How can i use the script on my poly mesh?

that depends on your script... which one it is... but usually just opening the .mel file in the scriipt editor and running it should be enough.