First : Make sure that you have the bios files needed in Retro Arch\System
Second : Make sure that you have installed the Duck Station core and pointed to your PS 1 roms.
Third : Do a test load from within RetroArch to make sure that the rom loads.
Fourth : In Attract Mode
Executable : Point to your RA set up folder making sure you use retroarch.exe at the end (always check skelling errors) In my case C:\Emulators\RetroArch\retroarch.exe
Arguments : -L "cores\duckstation_libretro.dll" "[romfilename]"
Rom Extensions : .zip;.chd;.bin and whatever else you have, if you only have .chd then no need for all the rest
All your other paths for art etc will be from your end so waste of time me listing those lot
Fifth : If things do not work, go back and check for any spelling mistakes, that you have added the .exe or ;
Hope this helps someone out, and saves having to go through a long list of threads just to get to one emulator. I think the other lists use expse or however you spell it and not RA.
Just to add if you do get any errors if you are using zip files, these might need to be unpacked or another PS1 core to be used.
Regards
Mark