sudo apt-get update
sudo apt-get install perl libnet-ssleay-perl openssl libauthen-pam-perl libpam-runtime libio-pty-perl apt-show-versions python
wget http://downloads.sourceforge.net/project/webadmin/webmin/1.941/webmin-1.941.tar.gz
tar -xzvf webmin-1.941.tar.gz
cd webmin-1.941
sudo ./setup.sh /usr/local/webmin

Note: You should download the latest version of Webmin.