You can skip this step if you bought your putty knife from iFixit. Putty knives purchased from iFixit come with pre-ground edges.

You'll need a putty knife in order to open the case. A 1.5 inch thin putty knife will work well, but you'll want to grind the edge down. Rub the putty knife's short edge back and forth on a sheet of all purpose rough grit sandpaper (100 grit will work fine) until it attains a beveled edge.

Place the mini upside down on a cloth and turn it so that the apple leaf faces you.

Insert the putty knife into the seam between silver outer case and the white plastic. If you have trouble, you can insert the putty knife at an angle or grind the knife's edge down further. Push the blade down until you meet firm resistance (roughly 3/8 of an inch).