Is this currently a feature? For whatever reason I also can't load up ghosts on the main Time Trial screen.
I used it only once, so I can't exactly remember, but you first have to select the ghost and then at the garage you would be able to select his setups.
Select the ghost you want to use and then click "Start" You will see your car standing on the race track and next to your car you see a window with the name of the Ghost you selected. Go with your mouse pointer to that window and you will see a little "wrench icon" turning blue. Click on it and that will load the ghost setup to your car.
