Go to "Create/Accessory"...
Unfortunately you can not detach like you could do in iClone.
Though you still can get what you want, it's just a bit tricky... Pull your car aside and make base pose for character.
Then pull car back as desired and as car is attached to hip, you still can move arms/head without moving the car...
Hope that helps...
Toystorylab on Vimeo : Crassitudes (my "Alter Ego") on Youtube: