Install Webmin with apt-get by adding the Webmin repository to your sources:
echo "deb http://download.webmin.com/download/repository sarge contrib" | sudo tee --append /etc/apt/sources.list
wget -q http://www.webmin.com/jcameron-key.asc -O- | sudo apt-key add -
Then install Webmin
sudo apt-get update
sudo apt-get install webmin
If firewall is enabled, allow traffic on port 10000
ufw allow 10000/tcp