Updated Readme with instructions

Signed-off-by: Tomas Fabrizio Orsi <[email protected]>

README.md

@@ -2,6 +2,19 @@
 My personal Gentoo overlay.
 Pull requests more than welcome.
 
+## How to enable the overlay
+Thankfully, the lemon-lime-overlay is part of [Gentoo overlay list](https://overlays.gentoo.org/).
+To enable, simply run:
+
+```terminal
+eselect repository enable lemon-lime
+```
+
+Before using it for the first time, you need to sync it:
+```terminal
+emaint sync -r lemon-lime
+```
+
 # Ebuilds in this overlay
 
 - tiburoncin: https://github.com/eldipa/tiburoncin