Loosen that black bolt, then remove the two bolts that hold the caloper on. Remove the caliper from the disc, then undo that black bolt to let the pads out. Is that a motorbike caliper?
Remember to pull out the spring clip before you undo the black bolt. Even though you will get a new clip and bolt in the Avid X0 pack try and keep them in case you lose one. Remember to prise the old pads apart before you remove them so that there is enough room for the new ones. The bolt is refitted with a very low torque and the spring clip stops it turning. I have the same bike as you (AMT Pro) and they can get through the organic pads quickly esp in rain and mud. On the back of my UK AMT Pro the rear caliber is sticky and even if I push it in it tends to bind. It needs some manipulation to get it free. It is not essential but I highly recommend that you remove the wheel before changing pads, you do not want to be levering against the disc.
I use either the Park Tool disc spreader or a large screwdriver wrapped in cardboard but the manual says to use a screwdriver in between the old pads to fully return the callipers.
i ordered the Sintered ones as had no organic in stock ;( see how long these last, im just going to take the callipers off and do it that way as looks easy enough and use a screwdriver to reset the pistons for the new pads.
May of had a small amount of contamination from oils or just need bedding in a bit I'm just waiting for a set of pads to arrive as I had a major foul up with mine