View attachment 671134
You need a pin (sewing kind, but not needle) Put it through the hinge and fold the end over. Snip the remainder of the pin off.
View attachment 671135
Here, there are two circles, one on top, one on bottom. The blade has a hole in it the same size as the circles. You need to gently pry the case apart enough to slip the blade past the circles. The circles will be completely inside the hole in the blade and act as hinge for opening and closing the blade.
You need the Accessory kit to complete the knife. The Accessory kit includes the black and white mask logo acrylic piece to glue in the knife. The kit also includes 2 of the keyboard stickers. (in case you make a mistake with one.) The Accessory kit is $10 which includes shipping.