Libretro and Leia

Guys, can any one help me out understanding how to manage libretro in Leia? Afaik libretro should have been included in leia, but even starting from scratch on various LE and CE releases, I can’t get it working.
I suppose that due to this integration IARL could work basically out of the box but that’s not the case.
Does anyone have an HOWTO step by step for noobies like me? Thanks😀