Here is a Tech Guide for Masterlink clip removal and reinstall procedure.  Turn the wheel until the masterlink is positioned on somewhere convenient on the rear sprocket.  Then, loosen your axle nut and adjust the chain tension to give it some slack.

Now, align one side of the pliers against the pin (shown above), and the other against the face of the open end on the clip. Got to be flush and level. Push inward to put pressure against the Masterlink as you squeeze the pliers. You should feel a little "click", and get this:

Then remove with your fingers like this:

Pull off the flat plate, push out the masterlink, and do your business.

Note: Never...NEVER....EVER....remove your clip by wedging a screwdriver underneath and prying out like this:

Nope...don't do that. It will deform the clip and cause it to either not work right upon reassembly, or fail (break) prematurely.

Now, for the reinstallation procedure just reverse the process. First, push the Masterlink on from the backside. Then slide on the plate...maybe squeeze it tightly with some pliers or a mini C-clamp.

Finally, install the clip.  Most importantly, make certain the closed side of the clip is pointed toward the front of the bike, and the open side of the clip is pointed toward the back of the bike.....when the Masterlink is positioned on the top rotation of the chain. This means the closed end of the clip rotates into the countersprocket FIRST. Not the open end. This keeps the clip from getting knocked off the link when rotating around the merry-go-round. Make sense? 

There are little grooves in the master link pins...slots where the clip goes. It is absolutely CRITICAL that you get the clip full engaged into those two slots.  I like to make absolutely certain the plate is pushed on far enough to expose these grooves for the clip attachment. One way I make sure, is by sliding on the clip and pulling it to the end on each separate pin like this:

Wiggle it around to make sure its seated in that groove real good. If you can't seem to get it, try removing the two little O-rings behind that flat plate (right or wrong, I threw mine away.....but kept the O-rings on the backside of the Masterlink). This made my life much easier....and I no longer feared removing my chain whenever I feel like it.  

 This is the point where most alleged masterlink failures are created.  People "think" they got the clip snapped into place correctly, but actually didn't.  Its on the pin, but not inside the groove.  If you look very closely at your clip (and compare to a spare clip) you can usually tell if its in the groove or not.  If it missed the groove, the clip will be spread out wider than normal.  Inside the groove, most clips are relaxed.   Take off riding with a clip not seated in the groove, and you're sure to loose it quickly.  Then, the results can become devastating....even life threatening at high speeds.  So, make absolutely certain you get this part right.  Its not hard....just needs extra attention.

Next up, remove the clip and get ready to reinstall like this:

Align the pliers on the back side of the clip and the the closest pin, then apply some pressure and squeeze the pliers until you hear it snap on like this:

Voila! The clip is safely and securely back on the Masterlink.  Verify it is seated "in the pin groove" and you're safe to roll. This procedure allows the clip to be used and reused many times without significant risk of weakening the clip. Just keep it flush against the plate and snap it on &/or off parallel to the plate (at all times).  Of course, its always best to use a new clip each time, if you have an adequate supply of them.

Extra clips are relatively inexpensive. I always buy extras and carry some on board, along with my spare Masterlink, as a backup plan. There's a reason for that, and it goes as follows:

Good decisions come from knowledge,
Knowledge comes from experience,
Experience comes from bad decisions.

Nuff said!