Login  as root and run the following command:

wget http://prdownloads.sourceforge.net/webadmin/webmin-1.350-1.noarch.rpm

Once finished run:

rpm -U webmin-1.350-1.noarch.rpm

The rest of the install will be done automatically to the directory /usr/libexec/webmin, the administration username set to root and the password to your current root password. You should now be able to login to Webmin at the URL http://localhost:10000/ .

Webmin install complete. You can now login to https://hostname.domain:10000/
as root with your root password.

NOTE: the default login and password is your root and root password. this is the same login you used with you ssh to your server or whatever your root password is, so your login will be like this:

Username: root
Password: xxxx (what ever your root password is)