I spray a little WD 40 on the clip, mash it down with a socket a few times to loosing it up. Sometimes, the the cap is hard to press because the clip is stuck to it. But it will loosing up. Then like they said, pry it out with a screw driver. There's a flat spot on the cap. Turn the cap until the end of the clip is in that flat spot. From there, I pry it up about half way, then use the needle nose to pry it the rest of the way while keeping my hand over it, just it case it slips from the needle nose.
Once you've got everything except the slip, like it's said earlier, take a socket (I used a 10mm) and tap it back in place.
It took me a few tries at first. And have lost a few of those clips. When they come off, if not secured or surrounded (by your hand), they FLY.