The icons, we use, are part of the awesome font.
You need to remember to google “cheatsheet awesome”.
https://fontawesome.com/cheatsheet
We navigate to this website and we are copy/pasting an icon from this website and we will show you a neat trick to find out the correct code for xmonad.
Check the xmonad.errors to see what the correct code is and copy/past it in the file xmonad.hs