Hello Ronald,
Start with a new team folder in the mod folder like \rFactor\GameData\Vehicles\BBSE_Mini\YOUR TEAMNAME
Edit an present .veh with you txt editor and change DefaultLivery, Number, Team, Driver, Description and FullTeamName to your values.
For your own PC you can paint or re-paint what you want. If you want to publish your Skin, you must start a new paint with the template.
greets
slomo