Okay so lets say you downloaded a car pack you will have the files for police , police2 ,and ect
the file named police goes for the cruiser the one that says police2 goes for the patrol you may use it how ever you like lets say you wanna put the police2 as youre police cruiser that will also work lets say you wanna put police2 as youre noose cruiser and ect just when it comes to the big vehicles like polpatriot you wanna make sure you download a vehicle meant for that slot you know like a suv or truck w.e .... hope I helped explain a little better if you have a specific vehicle you downloaded and you don't know what to replace it with or as where it goes just let me know .