Here’s some commands (see video for more instructions);

sudo nano /lib/systemd/system/x11vnc.service 

[Unit]
Description=x11vnc service
After=display-manager.service network.target syslog.target

[Service]
Type=forking
ExecStart=/usr/bin/x11vnc (your switches)
ExecStop=/usr/bin/killall x11vnc
Restart=on-failure

[Install]
WantedBy=multi-user.target

systemctl daemon-reload
systemctl enable x11vnc
systemctl start x11vnc

and if you want to see if it’s working ok try

systemctl status x11vnc