After sliding the clip COMPLETELY out of the way, and pulling the slide back 1/4 inch, you should be able to lift it straight up. If it is giving you troulble, wiggle it around a little while pulling back on it and see if that helps.
The ones I own have always come apart easily, hopefully yours is just a little stiff from being new.
The ones I own have always come apart easily, hopefully yours is just a little stiff from being new.