Here is how you take the buckle apart I am pointing to where you have to pry. Carefull they crack/break easy!
This is the notch in the back of the cover
And the matching notch on the buckle
Here is the notch on the side that you are prying it apart for
And the matching notch in the plastic cover
Here is the button in the cover. Note the metal part in the front. It is in wrong
Here is how the metal piece is supposed to go.