You have to place nodes where you want your wheels to be, you can do this by hovering over the 3D view, press Shift and A, go to 'Empty' and select 'Single Arrow', create four of these for each wheel, then move the arrows to where you want the wheels to be, then name the arrows 'hub0' (front-left wheel), 'hub1' (front-right wheel), 'hub2' (back-left wheel), and 'hub3' (back-right wheel')
If your wheels aren't rotated correctly in-game, try spinning each of the nodes by 90 degrees
Also, make sure the origins of your objects and nodes are centered onto the grid, you can do that by selecting everything with A, press Shift and S, then select 'Cursor to Center', then press Shift, Ctrl, Alt and C (great hotkey, i know), and select 'Origin to 3D Cursor'
This will make it so that none of your objects spawn or appear weirdly in-game