Step 1: Drop vehicles.meta in dlc.rpf\data

Step 2 : Drop the Data folder in dlc.rpf\x64\data\lang (this file will be read automatically when you start the game)

Step 3: Drop the dlctext.meta in data folder, and them the content.xml in dlc.rpf

Step 4: Drop the texture (ytd file) into the dlc.rpf\x64\vehicles.rpf

Done! Enjoy!