Install

Prometheus itself

pacman -S prometheus    # Archlinux
pkg install prometheus  # FreeBSD

Prometheus exporters See prometheus exporters.

pacman -S prometheus-node-exporter  # Archlinux
pkg install node_exporter           # FreeBSD

Enable

systemctl enable prometheus.service  # Archlinux
sysctl enable prometheus             # FreeBSD

You probably want to use ntpd on the server, and all client OS's so time-relative queries are accurate.