I cant get single player to work with custom vehicles

As the title says, I just got gta 5 on pc and I am trying to get lspdfr to work with custom vehicles and I cant. I followed different videos and stuff but when I go to download I think it is Open IV i cant and then I went and found a different place to download it and I got it to work but when I tried to load up Rage plug hook. It starts to load but then it says it failed due to open IV