Push in the black tab found 1/4 ways down on the inner left side of the frame. (healthchecksystems.com)
Using a staple gun, staple the back side of your frame's corners. (homemadelovely.com)
An A / B comparison with the DVD reveals a hair more information on all four sides of the frame here, though the improved colour reproduction is far more readily apparent. (filmfreakcentral.net)