That command only installs the package wlr-randr. You use it in terminal (Konsole in KDE Plasma). Start with running wlr-randr --help. I’ll look at this on my old ASUS notebooks (in Plasma desktop) when I get some time. I don’t know much about this package except that I think it is a substitute for xrandr. Whether it works in OMLx is unknown until people test it.
Edit: See this. At this point we should hope for help from @AngryPenguin and/or @TPG.