I agree that the video isn't as helpful as it could be, at least with regards to the first step in separating the case. The confusion for me is that I've had a LOT of cases like this over the years, and sometimes they're two pieces and sometimes they're three. (Two hard plastic halves, with a rubber gasket that goes along the outside. This was true for some Otterboxes I've had before.)
But, when I realized the rubber gasket/bumper was part of the bottom half of the case, it made it easy to know where to put pressure and pull the separate and open the case.
Of course, once it's separated, it's perfectly clear, and putting it together again is easy.
Hope that helps someone else who's a bit unclear and who doesn't want to chance ripping or breaking their new case.
Beyond that, the case is really nice and fits my Nexus 6 perfectly. I think it will add lots of protection, and the belt clip is sturdier than I thought it would be. :)