A better explanation of how to split a jewel case than what I’ve seen so far on the web.
To begin with, it can make it easier to remove the case lid (although it’s not necessary). The lid is attached with pins that you can flex outwards to pull apart.
With the actual case inset, the important thing to note is these pins holding it:
You’ll need to pull the pins out of their slots, and then move the inset up and out of the case while the pins are clear. I find it’s easiest to start on the outside pins. So slide a nail in between the inset and case at the blue mark and try to hold them apart; at the same time get a nail underneath the case floor at the green mark and when the pins are clear, pop it up and out of the case.
Now do the same on the other side. I usually hold it at these points:
When it’s clear at all the pins, it should come up freely.
After replacing the paper or whatever it is you’re doing, putting the inset back in is much easier. It should just snap into the right place.