PiRetrocade Assembly Guide
LightningHawk 
Emulation Software
In the video above you saw how easy it was to get up and running on your gaming machine. Let's take a look at what's going on inside.
Besides powering the Pi and restarting the Pi after adding ROMs you will not have to do anything else to get started playing games. The Image on the SD card is called Porta Pi Aracde and is a collage of several programs compiled by Ryan Bates at Retro Built Games. The image contains RetroPie, Emulation Station, RetroArch and Retrogame.
Power the Pi, and connect a monitor through an HDMI cable. Once it boots up you should see the RetroPie home screen, then the Emulation Station home screen and then a menu which shows you the available system emulators and how many games you have in each emulator. Now is when you'll want to get familiar with navigating through the menu and add your roms. You can fully navigate through the menus with your newly assembled gamepad, or you can use a keyboard.
A Little Background on the SD Card Image
If you need a fresh copy of Porta Pi arcade click the button above to navigate to Retro Built Games downloads page.
RetroPie is backbone of your retro-gaming machine. It can be installed on top of an OS like Rasbian. We left off the OS so you can decide which one you'd like to add or if you need one at all.
If you decide to add an OS, you can exit the emulator, and enter the Linux GUI by pressing F4. This brings you to a terminal window, and typing the command sudo startx starts the GUI.
To get back to the emulator, log out of the Linux GUI, and type the command emulationstation in the terminal window.
Without Rasbian the only commands you need are the F4 key to enter terminal window and emulationstation to return to the emulator.
Emulation Station is the graphical front end that gets you easy access to your favorite retro games without a keyboard. Once you have built your controller, you will have all the buttons necessary to navigate through Emulation Station and play your legally obtained roms.
RetroArch exposes the functionality of a game or emulator. It is the front-end for libretro and can do things like raw video recording and netplay. It also allows for universal controls to be programmed -- it currently is for this tutorial. This means that the controls set for ESC, Enter, Jump, Shoot, etc. are seen across all games in all emulators - you won't have to set up your game pad every time you enter a new emulator.
Retrogame is a great tool which allows Raspberry PI GPIO-to-USB utility for emulators written by Phil Burgess for Adafruit. This is how the button mashing gets registered as keyboard presses. To change where the buttons are mapped to or to add more buttons head over to Retro Built Games .
Adding Roms
The easiest way to add roms is to use a USB Thumb Drive or SD Card with adapter. Format the USB drive to get a fresh drive. Add a folder called 'retropie', and insert it into your Raspberry Pi 3. Wait a few minutes, or look for the flashing light on your USB to stop.
Pull out the USB drive, and plug it back into your computer. The 'retropie' folder will now have three sub folders: 'BIOS', 'Configs' and 'roms'. Save your roms into the appropriate folder within the 'roms' folder.
Put the USB drive back in the Pi, and wait once more for the file transfer to finish. The roms are automatically saved to the correct emulator folder. You now need to restart your Raspberry Pi.
Plug in a keyboard, and Hit F4 to exit emulation station. From the terminal window, type the command sudo reboot to restart your station. You should now see the menu expanded based on the roms you saved. Thus, if you added NES roms, there will now be an NES option in the menu. Instructions on obtaining roms is beyond th scope of this tutorial. You should only be adding legally sourced roms onto your Raspberry Pi gaming station.
Test
Once you have your buttons placed, the wiring finished and your roms installed, it is time to test your gamepad. Power your Raspberry Pi, and wait for the emulation station menu screen. Use the joystick to navigate through the different emulators. Button A will act as select or Enter in the menu, and B will act as a back button. The select button is escape for when you want to change games and get back to the main menu from within a game. From within a game A, B, & C will act as the normal fight and special buttons.
If you want to change the keyboard mapping, add a player 2, or add a coin acceptor head over to Retro Built Games and check out the Porta Pi Tips for extra help or inspiration.
For more in-depth instructions on how to get started with RetroPie, check out their extensive guide found on GitHub.