Webmin is a web-based interface for VPS admin. You can set up user accounts, Nginx, DNS, file sharing and much more. Webmin removes the need to edit Unix configuration files like /etc/etc/ and lets you manage a system from the console or remotely. I look at Webmin as a hybrid between a simple "finder" or explorer, a FTP and a monitoring software. You can manage your VPS and upload files and Debian updates.
First time you connect to the VPS, you have to use your Terminal of choice. Enter your ssh command and your VPS password that you got from Upcloud (or other vendor). Then use the Terminal to install Webmin. You may need the Terminal for installing other stuff, but most commands can be done by the built-in "terminal" in Webmin. You can even store "one-click-command" in Webmin (Like restart services).
ssh email@example.com (replace this IP address with your-vps-ip)
These commands are picked from Webmin source. But my comments are added. Begin with the command:
then run the command:
dpkg --install webmin_1.974_all.deb
Debian will complain about missing dependencies, and you can install them with the command:
apt-get install perl libnet-ssleay-perl openssl libauthen-pam-perl libpam-runtime libio-pty-perl apt-show-versions python unzip
You may need some other commands to complete or clean up the installation. Read the terminal "errors"
You should now be able to login to Webmin at the URL https://your-vps-ip:10000 - with some initial warnings (ignore).