Place "o2rom.bin" (required) in your RetroArch/libretro "System Directory" folder, in Miyoo in folder .retroarch/system.
You have to add the roms in the roms/odyssey folder in .bin format
In some games, like "Ufo" or "Alien invaders" to play the Mapped Port 2 is used.
Once you start the game, when you go from the "Select Game" screen, you have to change the controller to port 2.
Open the menu, with Reset, you will get the "Quick Menu" menu, in Controls -> Port 1 Controls -> Mapped Port change it to 2. In order to start playing, passing the "Select Game" screen must be Mapped Port in 1.
To return to the game in "Quick Menu" you give "Resume"