1. Unpack the contents of the file straight into the game folder, so that the r6 content will be added into the existing r6 folder
2. Open the CET console in the game and enter the following commands:

Game.GetVehicleSystem():EnablePlayerVehicle('Vehicle.v_utility4_kaukaz_bratsk', true, false)
Game.GetVehicleSystem():EnablePlayerVehicle('Vehicle.v_utility4_kaukaz_bratsk_concrete', true, false)
Game.GetVehicleSystem():EnablePlayerVehicle('Vehicle.v_utility4_kaukaz_bratsk_container', true, false)
Game.GetVehicleSystem():EnablePlayerVehicle('Vehicle.v_utility4_kaukaz_bratsk_dumpster', true, false)
Game.GetVehicleSystem():EnablePlayerVehicle('Vehicle.v_utility4_kaukaz_bratsk_machine', true, false)
Game.GetVehicleSystem():EnablePlayerVehicle('Vehicle.v_utility4_kaukaz_bratsk_metalstud', true, false)
Game.GetVehicleSystem():EnablePlayerVehicle('Vehicle.v_utility4_kaukaz_zeya', true, false)
Game.GetVehicleSystem():EnablePlayerVehicle('Vehicle.v_utility4_kaukaz_zeya_freight', true, false)
Game.GetVehicleSystem():EnablePlayerVehicle('Vehicle.v_utility4_kaukaz_zeya_full', true, false)
Game.GetVehicleSystem():EnablePlayerVehicle('Vehicle.v_utility4_kaukaz_zeya_barrels', true, false)
Game.GetVehicleSystem():EnablePlayerVehicle('Vehicle.v_utility4_kaukaz_zeya_container', true, false)
Game.GetVehicleSystem():EnablePlayerVehicle('Vehicle.v_utility4_militech_behemoth', true, false)
Game.GetVehicleSystem():EnablePlayerVehicle('Vehicle.v_utility4_chevalier_centurion_flatbed', true, false)
Game.GetVehicleSystem():EnablePlayerVehicle('Vehicle.v_utility4_chevalier_centurion_cargo', true, false)
Game.GetVehicleSystem():EnablePlayerVehicle('Vehicle.v_utility4_chevalier_centurion_poor', true, false)
Game.GetVehicleSystem():EnablePlayerVehicle('Vehicle.v_utility4_militech_behemoth_netwatch', true, false)
Game.GetVehicleSystem():EnablePlayerVehicle('Vehicle.v_utility4_kaukaz_zeya_kurtz', true, false)