1- Choose which tyres you want to use.
2- Choose which car you want to use the tyres on.
Copy files in that folder to:
.../content/cars/YOUR CAR/skins/SKIN

All tyres will work best with these cars:
Set 1-Evora GX, Evora GTC
Set 2-MOD- Gallardo GT3, CORVETTE C7R, 599XXEVO, MOD- F430 GT3
Set 3-MOD- R8 LMS (r8_lhm)
Set 4-MP4 12C GT3, 458 GT2, McLaren F1 GTR, 235i Racing, Nissan GTR GT3, MOD- 997GT3RSR
Set 5-SLS GT3
Set 6-Z4 GT3, M3 GT2

PS: Green GT Bonus Tyre is only for Set 4 .