Ok, I got this from the “http://emulation-general.wikia.com/wiki/Using_RetroArch”
“You can also set the libretro path using the RGUI. In Retroarch, go to Settings -> Path Options -> Core Directory and navigate to the appropriate folder. If you set everything up correctly, you should see the cores when you select the Core option in the RGUI.”
I tried all that but still no cores. I wonder if I have to start from scratch?