Alright so you might already get the gist of how to do this but it is really cool. First, you need a small screwdriver because most calculators have really small screws. If you have a bigger screwdriver it also works,but it is kinda hard to do and ruins the screws. Besides you might want those screws for later projects(FREE SCREWS YAY!!!).
Step 1: Unscrew and Unhinge Everything
The picture above show that what you get after you do that. After you do that break of the parts until you get figure 2.
P.S.-My pictures are flipped so the right is on the left and the left is on the right. (If that makes sense :/)
Step 2: Glue and Tape
Now you think you are done but not quite. The Keyboard of the calculator needs to be glued to the thing that is behind it with all the cool patterns. Then tape the battery to the back of the screen. Then customize with whatever you think is suitable for it. :)