Install 2.8" PiTFT
The first component we need mount to the case is the display screen. Before we do that, we'll need to insert the PiTFT rubber buttons into the case. Place them over the cutouts from the inside of the top case and press them into place.
Now that the PiTFT button actuators are in place, lay the PiTFT screen over the case. Line up the mounting holes with the standoffs. Then, insert #4-40 3/8 sized machine screws into each mounting hole and fasten them into place. Be careful not to apply excess force, and fasten slowly.
Install Gamepad PCB
Next up, let's fasten #4-40 3/8 sized machine screws into the mounting holes on the corners of the gamepad PCB. Insert them from the top of the PCB so that they're just barely protruding from the back side. This makes it easier to mount it to the standoffs in the case.
Now, insert the rubber D-Pad, Action Buttons and Pause/Start actuators into the cutouts of the top case part. Place the gamepad PCB over the standoffs and line them up with screws. Slowly (and carefully) fasten the screws into the standoffs. However, DO NOT fasten them all the way through! Only fasten them down until they're deep enough to be lower than the height of the case. Please reference the photo - if screws are inserted too far, they could protrude through the surface of the case.
Connect Pi Cable
Next, we can install the Pi Cable to conenct the Gamepad PCB to the PiTFT display. The orientation of the Pi cable is important, so reference the photo and follow the markings.
Now our PiTFT display and Gamepad PCB are mounted to the case. Press the buttons on the PiTFT and Gamepad to test them and see they feel good. If the buttons get stuck, the gamepad isn't flush with the standoffs.
Let's go ahead and pop the speaker into the case. Lay the speaker over the cavity with the grill and press it down to snap it into place. The wire should be oriented in a position so it's not in the way of the corner standoff.
Shoulder Button Mount
Next up we need to mount our two shoulder buttons to the shoulder mounting piece. To do that, we can use adhesives such as E600 or hotglue - But I've found using mounting tack works just fine (plus, it makes it adjustable if we don't position it correctly the first time around). Add the tack to the back of the 12mm button and position them over the two recessed square spots on the mounting part. Press them down to stick them into place.
Shoulder Button (cont.)
Fasten four #2-56 3/8 into the standoffs of the shoulder mount. Screw them in until the barely protrude the standoff - this is going to make it easier to mount it to the case. Next, insert the rubber shoulder button actuator into the cutout of the bottom case part.
Install Shoulder Button Mount
Place the shoulder mount over the standoffs on the bottom case. Make sure the screws line up with the standoffs - they're position / orientation specific. Once they're lined up, carefully fasten the screws down. Here, you can fasten them all the way.
Now if a good time to insert the slide switch into the bottom case. Take note of the OFF position of the slide and install it to your liking (I prefer down is OFF, up is ON).
Install Raspberry Pi 2
Next up, lets mount the Pi to the bottom case. First, let's fasten #4-40 3/8 sized machine screws to the two mount holes on the back of the bottom case part. Like the previous mounting standoffs, fasten the screws so they're just barely protuding through the top of the standoffs. Then, lay the Pi over the standoffs and line up the screws with the mounting holes. Once in place, fasten the screws all the way until they're flush with the surface of the case.
Mount PowerBoost 1000C
We'll need two #4-40 3/8 machine screws to install the PowerBoost to the case. Fasten the screws to the two mounting holes of the PowerBoost - This will create threads. Once they're made, lay the PowerBoost over the standoffs (close to the center bottom). Hold the PCB in place while fastening the screws to the standoffs. Don't fasten these screws all the way through, just deep enough they go past the heigh of the case - similar to the other components.
Insert and fasten a single #4-40 3/8 machine screw into the mounting hole of the amp PCB (should be the hole closest to the Adafruit logo) - This will help create the screw threads. Then, place the PCB over the standoffs and hole it down to fasten the screw into the standoff.
Grab the lipo battery and plug in the JST connector to the JST port on the PowerBoost 1000C. Flip the slide switch on, and see if the circuit works! The blue LED indicates the battery is charged and the circuit is powered on.
If the LED doesn't light up, you either have a defective PowerBoost, or a short. You'll have to double check your wiring for short using a a multi-meter. If you have any issues or questions, please post it on support forums at http://forums.adafruit.com/
Install Lipo Battery
Now we can install the 2000mAh lipo battery. A good spot for it is right behind the PiTFT display. To keep it in place, we can use a piece of gaffers tape. Try to keep it up closely against PiCable. Position it like in the photo, closer to the right side to avoid intersecting with some of the components from the Pi.