Go to http://underground.tiera.cc/lfs_skins/
Log in with your pereulok account (the website is slow give it some time)
Click the button Choose And browse to your skin and click the button next to "choose"
The skin name must be CAR_SKINNAME (example FXO_MYSKIN)
Also the dimensions must be maximum 1024x1024 or less ( NOT 512x1024 or 2048x2048 etc)
After you uploaded the skin , place it to liveforspeed/data/skins
In pits press new colours select your skin and there you go !