Addon:

First, go to gta5 / mods / update / x64 / dlcpacks

Drag the "redeye" folder there.

Then, go to gta5 / mods / update / update.rpf / common / data

Edit dlclist.xml, add "<item>dlcpacks:\redeye\</item>"  above "</Paths>"

Make sure to save.

To spawn the car ingame, use a trainer to spawn by spawn name.
Spawn Names: 

Widebody: redeye
Non-Widebody: redeye2
Rally Raid: redeye3

To make sure your game doesn't crash, download and install a custom gameconfig such as:
https://www.gta5-mods.com/misc/gta-5-gameconfig-300-cars



