To install xmonad just follow these instructions.
sudo apt-get install xmonad
Which will install xmonad and any other packages on which it depends.
|Maintainer||Debian Haskell Group <firstname.lastname@example.org>|
|Description||Lightweight X11 window manager written in Haskell Haskell. Windows are managed using automatic layout algorithms, which can be dynamically reconfigured. At any time windows are arranged so as to maximise the use of screen real estate. All features of the window manager are accessible purely from the keyboard: a mouse is entirely optional. Xmonad is configured in Haskell, and custom layout algorithms may be implemented by the user in config files. A principle of Xmonad is predictability: the user should know in advance precisely the window arrangement that will result from any action.|