How do I use it with vehicles that come with one? I know it goes in the scripts folder but don't know how to activate it in game.
If it's a '.cs' file ('LAZERHelper.cs' for example) you just drop it into the 'scripts' folder & it should work automatically if it's set up correctly.
You can open & edit a '.cs' file with a text editor (like Notepad or Notepad++). Worth having a look inside them & making sure the name is correct for the plane you are using it with. If not, change all references to the other plane to the name of the one you are using it with
Point me to the download/s you're talking about & I'll download it/them & have a proper look