I don't have that case, but the flip case, you need a paperclip or something like that and push down in the little hole toward the top of the clip, that will release the clip, then just slide down.
Sorry for the quality of the pics, but I made these up really quick - hope this helps -
Here is the case without the clip. The button to the right of the arrow is what you push down to release the clip.
With the case on, I push down with the tip of a ballpoint pen where the arrow is, in the small hole, while sliding the clip towards the Marware logo. It can be tricky, but just make sure you keep the button depressed while you slide it. Good luck!