You don't need to be an admin to spawn a vehicle. To spawn a vehicle:
While ingame, press B
Hit Special Tab and on the bottom, you'll see a Vehicle Spawn brick.
Select that, then hit the slot you'd like the brick in.
Press the assigned brick slot button and place the brick (If you don't know how to place bricks, someone else will explain...hopefully)
Press Q and scroll to (or press the assigned slot move keys) to the wrench.
Hit the brick, a GUI will appear. In the place saying NONE, click it.
Select a vehicle from the list, then hit OK.
Vehicle!