Hi can you explain to me where to copy the rullset folder or its contents? The music works, but I can't do well with the audio in the rullset folder
You just need to unpack archives into "mods" folder and enable these mods in the game.
"mods" folder can be found in your documents folder: \Documents\OpenXcom\mods. Place files from an archive there, just unpack archives in this folder, so you'll have PSXMusic, PSXSFX, PSXVideos (if we talk about ufo:eu). Then start the game and press "mods" button in the menu. Locate PSX sound mods in the list (at the bottom) and enable these mods clicking on them.
Also, you can read README.md in game folder for more info about folder locations.