Install AlphaPanel, and find your way around it.
AlphaPanel installs on a bare Ubuntu server with one command. Run it as root:
curl -sSL https://licenses.alphaxp.net/download/setup.sh | sudo bash
The installer sets up nginx, PHP, MariaDB, mail, the firewall and the panel itself, then prints the URL and the password it generated for you. It takes about ten minutes on a fresh box.
A screenshot of every screen is on the tour.
This page is yours to edit — open Content in the panel, find it under Pages, and write whatever your users need. You can add more pages there and link them from the navigation.