This pic might help - it's the rear subframe as seen from the front (imagine you're the fuel tank). The upper arm bolt heads are in those two holes.
As others have said, you'll need a short 1/2" extension -
this one will do it. The two bolt heads you can see are the lower arm bolts.
Here are the 2 captive nuts, as viewed from above (imagine you're the car floor). Give them a
really good soaking with Plusgas before attempting to undo the bolts, otherwise you risk them spinning. If that happens it's a subframe off job.