Downloading

• sudo pacman -S xmonad xmonad-contrib

Also download the terminal

• sudo pacman -S rxvt-unicode

Starting xmonad with startx command

• sudo pacman -S xorg xorg-xinit
• sudo cp /etc/X11/xinit/xinitrc ~/.xinitrc
• sudo vim ~/.xinitrc

Remove lasts lines and add

urxvt &
exec xmonad && 

• Bobo recomendation, instead of just opening the terminal consider opening with neofetch to be more beutiful: urxvt -e sh -c 'neofetch; exec bash' &

• startx