Hi, you're missing only one of the rubber boots.
The pads are held on by the caliper. You have to undo the bolts on the sliding pins (remove those pins from the caliper that I can see on the right of the photo), put the pins into the caliper carrier (with the rubber boots), then put the pads in to the caliper carrier, and then fit the caliper over them so that the small rivetted-on springs are pressing the pads against the back of the caliper carrier.
A picture from me would be worth a thousand words, but I've gotta go right now. Hope you get it sorted and remember to Loctite(tm) the bolts into the sliding pins. Also grease the pins with coppergrease.
Pad change can be done by unbolting only the lower sliding pin and swinging the caliper up. Just for reference...
Cheers,
-Alex