Installation of webmin is very simple

Login via CLI (SSH) and type:

cd /etc/yum.repos.d;wget http://www.webmin.com/download/rpm/w...urrent.rpm;rpm -ivh webmin-current.rpm;ls

It will download latest Webmin repo, and extract it. Then you install the repo / webmin by:

rpm -ivh webmin-1.620-1.noarch.rpm

may take minute or two

Then login via web browser: http://yoursiteipORhostname:10000
Login credentials are your server username and password.

----

Uninstallation should be even simplier.
rpm -e webmin
OR
sh /etc/webmin/uninstall.sh