On the Drivers&Staff menu, next to "Active Drivers" there should be a button that says "Change drivers".
Once you press this, you will be see a list of all the drivers your team currently has.
Selecting one of these drivers will automatically assign them car one - selecting two will put them in the order they appear in the list.
If you would like a certain driver in car 1, only select that driver, and another driver from the list will be assigned car 2.
