Dolphin Emulator Cheat menu not working on gamecube

Does anyone know how to open and use cheats in Game cube games? I want to play metal gear solid twin snakes with AR Codes. I am able to load the game from hyperspin, then control alt delete to open dolphin itself. From there I can tweak graphical settings but as soon as I try the cheat menu it says the game must be closed to access this menu. So I close the game and then dolphin automatically closes also. I then tried going into the emulators folder to open dolphin thinking I can tweak the settings there before opening twin snakes. However only wii games show up at listed games I can open. I could not find any game cube games in the dolphin emulator. The was able to find the metal gear game file but its path wasn't to a dolphin emulator so it seems. Does anyone have any advice for finding and opening GameCube games in dolphin to use the cheat menu?