Use retroarch for rom games

I had a quick Google and found this post.
[LibreELEC] Run RetroArch on your S905/S905X device! - FreakTab.com

Not tried it myself as only got my A95x a couple of days ago. May give it a go sometime.

Quote from ram.khakurel

Hi,i have installed both the addon zips in my s905x tx5 running kszaq 7.0.3.010 32 bit libreelec,from that post.
When i run retro arch and go to menu,i can navigate with remote arrows but unable to select using ok button in remote.
Any idea?also dont know how to add rom and play.

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Sent from my iPhone using Tapatalk

The select button is x on the keyboard and arrow keys to navigate.
Plug in a usb keyboard navigate to input and map your game controller.
Starting a game/rom you need to download and select the core first and then open your rom.

Good afternoon.
Please tell me how to add Emulationstation in Kodi. As it has done in Retropie.