Put it in <code>~/.xmonad/xmonad.hs</code>, then restart Xmonad (Mod-q be default). This configuration file is the default configureation configuration file, plus a few changes. The mode key is moved from Alt to Super (windows key), the defalut default terminal is set to urxvt instead of xterm, and the PrtSc and Ctr-PrtSc are mapped to scrot (see below for details). Note that this file is written in Haskell, and thus, comments are --. This file also starts xmobar (Xmonad's bar). It is usually a separate package, so if you want this bar, make sure to install it and configure .xmobarrc.