Let me see if I can describe this in words only....

You need to pull the black plastic clip up away from the metal clip. It will slide up the strap. After that the metal clip -should- slip over the lug on the camera body. The clip is made up of two pieces of metal both of which the strap passes through. The outer piece of metal will slide back away from the camera lug hole. On my strap the metal clips cover, the flat part that is on the outward facing side, was just a little too long. It interfered with the camera body lug and wouldn't allow the strap clip to go on. I had to use a decent amount of pressure to get that outer part to snap behind the body lug. I used a small screwdriver to push on it, just behind the lug. A better way might be to get a small file and file a small relief to allow it all to go together easily. So, once the clip snaps in place you pull that plastic part back down the strap. It will fit into the metal clip, right behind the lug and will act as a lock to keep the whole thing securely locked down.
Pictures do speak a bunch of words so here's a couple quick ones of one of the mounted lugs....