I need a full guide on how to add skins...
Everytime I add a skin from lfsmods.com they are either not working at all... or they work but there is like see through bits everywhere and it looks really bad.

Whats wrong?

The things posted on that site aren't normal "skins", they are (as the name of the site suggests) modifications that change the shape of the cars. Since those mods aren't approved by the devs, discussion about them is not allowed on here, sorry.