Install webmin

http://www.cyberciti.biz/faq/freebsd-installing-webmin/

To install webmin, update your ports, enter:
# portsnap fetch update
Install webmin from /usr/ports/sysutils/webmin, enter:
# cd /usr/ports/sysutils/webmin
# make install clean

Configure webmin

Now, webmin is installed. Start webmin on startup, enter:
# vi /etc/rc.conf
Append following line:
webmin_enable="YES"
Save and close the file. You need to run /usr/local/lib/webmin/setup.sh script in order to setup the various config files, enter:
# /usr/local/lib/webmin/setup.sh
Sample output:

***********************************************************************
*            Welcome to the Webmin setup script, version 1.420        *
***********************************************************************
Webmin is a web-based interface that allows Unix-like operating
systems and common Unix services to be easily administered.
Installing Webmin in /usr/local/lib/webmin ...
***********************************************************************
Webmin uses separate directories for configuration files and log files.
Unless you want to run multiple versions of Webmin at the same time
you can just accept the defaults.
Log file directory [/var/log/webmin]: [Press Enter]
***********************************************************************
Webmin is written entirely in Perl. Please enter the full path to the
Perl 5 interpreter on your system.
Full path to perl (default /usr/bin/perl):  [Press Enter]
Testing Perl ...
Perl seems to be installed ok
***********************************************************************
Operating system name:    FreeBSD
Operating system version: 7.0
***********************************************************************
Webmin uses its own password protected web server to provide access
to the administration programs. The setup script needs to know :
 - What port to run the web server on. There must not be another
   web server already using this port.
 - The login name required to access the web server.
 - The password required to access the web server.
 - If the webserver should use SSL (if your system supports it).
 - Whether to start webmin at boot time.
Web server port (default 10000):  [Press Enter]
Login name (default admin):  [Press Enter]
Login password: [type password]
Password again:
Use SSL (y/n): y
***********************************************************************
Creating web server config files..
..done
Creating access control file..
..done
Creating start and stop scripts..
..done
Copying config files..
..done
Changing ownership and permissions ..
..done
Running postinstall scripts ..
..done

How do I view webmin?

Fire a webbrowser and enter url:
https://your-domain.com:10000/
OR
https://your-server-ip:10000/