Put it in <code>~/.xmonad/xmonad.hs</code>, then restart Xmonad (Mod-q be default). This configuration file is the default configureation file, plus a few changes. The mode key is moved from Alt to Super (windows key), the defalut terminal is set to urxvt instead of xterm, and the PrtSc and Ctr-PrtSc are mapped to scrot (see below for details).