The next thing you're going to do is fit 2 in the trunk. One will go behind the strut bar, and the other will go where the spare wheel is kept.
If you left the spare in the car like I did, you will then put the spare on top of the wheel that is in the spares location
Finally, if you left all the trunk material in the car like me, you will fold the floor mats up and put them in the corner of the trunk. I put them behind the passenger seat. This was a bad idea. Put them behind the drivers seat. and the hard piece will cover the spare.
Voila, 4 extra wheels in the Z