For rFactor2 you also have 2 ways
1:
Start Single Player
Select All Cars and Tracks
Select Track and Car you want
Click on EDIT SETTINGS
Click on AI you want in OPPONENT FILTER list
To remove AI click on "Remove All" at bottom of OPPONENTS list
2:
Open your STEAM\steamapps\common\rFactor 2\Support\Tools
Run MAS2_x64 or MAS2 for 32bit OS
click on the 6th icon on toolbar " Create the package file"
click "Create New Mod Package"
Put name for your "Mod" then click "Next"
Click on Location you want in your mod then click "Next"
To select multiple locations and vehicles hold Ctrl
Click on Vehicles you want click "Next"
Click "Done"
Click "Package"
Click "Install"
Little red box will turn green
Start rFactor2
Click on "Select Series"
Click on your "Mod"
You can select individual layouts and skins
*** When you select Locations and Vehicles make sure
you never check boxes in the left hand column
Always check the size of the mod in the top right corner
of "Create Mod Package" in MAS2 tool. It should be 5kb.