Ok, being a rear caliper, there is the added complication of the handbrake mechanism auto-adjust to worry about. First, pull the caliper towards you to push in the piston (it won't go far because of the handbrake mechanism). Undo the bolts that hold the caliper and its carrier to the hub, and remove caliper, carrier and pads as one. At this point, change the disc if necessary. Now comes the trickier-than-fronts bit. You either need strong thumbs, or a caliper rewind kit (about £15 from Halfords - be careful to get a Fiat one since others may be threaded the wrong way around). Remove the old pads, then use either the tool or your thumbs to twist the piston as you push. Once fully rewound, you may replace the pads (with a little backing grease, ensuring the nipple on the inner pad goes in the gaps on the cross of the piston). Slide the caliper back into place over the disc and resecure. Pump the footbrake and apply the handbrake a few times to let it auto-adjust and then test as you normally would.