How do I change my online car setup in NASCAR Heat 2?

https://support.nascarheat.com/customer/portal/articles/2872906-how-do-i-change-my-online-car-setup-in-nascar-heat-2-?b_id=16861

When creating a lobby turn Stability Help Off and Allow Custom Setups. You will then be able to create and change your Custom Setup in the Garage on pit road.