Is there a step by step manual on how to install and use a psx emulator?

Search for the game starter add-on repository on giithub

Your best bet is game starter if you r mostly into Libreelec as a media player as you don't have to reboot to another operating system...additionally you can incorporate your roms into kodi....basically you add a section to your skin for games and launch games directly from their as like you'r gonna play a movie from AEL addon...you can use also Emulation station....both addons launch games trough Retroarch..

And while playing you r still using the Libreelec OS in the background..and configs should still be working like mounts and scripts you have like systemd...probably even tvheadened recordings...need to try that soon..

Quote from thomaz

everythings installed from game starter but when i run emulation station or retroarch it asks me to quit kodi and when i hit "yes" ce 8.90.1 just reboots.

What are you running it on..is it a Rpi?

Before you try ES or anything else I would first make sure retroarch is working and launching the roms..as the other addons needs retroarch to work...If you r on LE8 go to retroarch settings and download cores.....then open retroarch and update assets..You need to get some roms to start with including their BIOS's..

ES doesn't work without roms in their appropriate folder

Sorry just seen ce 8.90.1 on your post...if that's the Core elec for amlogic don't think you r gonna make it work..this is for Raspberry Pi's and Generic