Ok, I don't have any PX brakes lying around right now, but you see the worn down part at the top where it came out, you need to get that under the metal part, there's kinda notch for it to fit into, it's hard to explain, you just gotta wiggle and wedge it into place - I usually use the end of the brake (the part the drags on the snow when they come off) to angle and wedge it around, and once you get it in the right spot, it just pops right in. You don't really need any other tools or levers, just pop it back in there.
There's a difference between this and bent, this is kinda like a dislocation, it can be put back in fairly easily by hand, where bending usually requires some sort of lever.