It really depends on what you want to do. Do you want to set up a server that serves up a specific directory for a specific user? Let's say you want to set up a module named "archive" that points to a directory "/usr/local/archive" so you can make sure you archive important data regularly. You can set up a user called "archie" with a group id of the same name if you want. This example below shows you what to put in /etc/rsyncd.conf. This is assuming the xinetd is set up properly and your firewall allows rsync from the client host to the server.
let's call the rsync server "serverA" and the archive repository "repoB".
With this example, on serverA, create a file called 'rsyncd.conf' in the /etc/ dir (i.e. /etc/rsyncd.conf) and edit it:
uid = archie
gid = archie
use chroot = no
read only = yes
path = /usr/local/archive
This will enable the client machine to connect to the rsync server as user archie and specify "archive" as the module which simplifies things a little.
On repoB if you want to rsync to a directory called "/var/serverA/archive, the rsync command would be:
rsync -av serverA::archive /var/serverA/archive/
And that should just about do it. Keep in mind rsync comes with a VERY useful man page as well so I would dig in there as well. I hope this at least gets you started!