This tutorial assumes that you have purchased a Fantastico license for the server you are installing it on. If you do not have one, you can obtain it from www.netenberg.com

cd /usr/local/cpanel/whostmgr/docroot/cgi
wget -N http://files.betaservant.com/files/free/fantastico_whm_admin.tgz
tar -xzpf fantastico_whm_admin.tgz
rm -rf fantastico_whm_admin.tgz

Now go to WHM, login as root and follow the link WHM -> Add-Ons -> Fantastico De Luxe WHM Admin (scroll down the left menu).

Upon loading, Fantastico De Luxe WHM Admin will auto-update your existing installation (if existing).

As for the setup, usually the defaults work fine for most servers. You will need to manually set up the update cron, notification settings, and phpsuexec option.