You need .Net scripthook and asi loader to run this script .
Just simply put carupgrade.net.dll and carupgradeimages folder in scripts folder.And ofcourse you can put carupgrade.ini but thats not needed for first time because it can create it itself with default keys.
What this mod does?
It creates some places where you can drive and upgrade vehicle like in GTA V Los Santos Customs.
More information here - http://xxproxxgammer.ueuo.com/Los_Santos_Customs_V1.1.php