Not every unit will need the glass front removed, but if fingerprints were mistakenly left at the scene of the crime, or more likely, you simply need to remove the front to add the crystals on applicable models, this can be accomplished by removing just four screws. These will only be accessible with the insert outside of the TV stand or frame, however.
On the left and right sides of the fireplace are curved metal wings. These are used to secure the insert into the mantle or TV stand. Along this piece at the top and bottom are screws, one at each corner, that hold the glass in place.
Using a Phillips head screwdriver, carefully unscrew these making sure that the front cover is held secure. The glass is held in place with a silicone and should not separate from the frame but this added precaution will help protect against scratching.
Once the front cover is off, insert the crystals and or clean the interior of the glass with standard glass cleaner and reattach.