Go to the link below adn download a .ZIP file with all the games compatible with this PCB, or go to the original GitHub post and see all the games. Then, open any game in Arduino IDE. Make sure that the "Arduino as ISP" programmer is still selected and the ATtiny85 board with 8MHz clock. Connect the Arduino UNO to the PCB at the ISP port, compile the code and click upload. The game will now upload to the ATtiny85. That's it! Play!