https://docs.newrelic.com/docs/servers/new-relic-servers-linux/installation-configuration/servers-installation-ubuntu-debian

new_relic.md

sign up for a new relic account first and you'd get the license key on your account page.

sudo sh -c 'echo deb http://apt.newrelic.com/debian/ newrelic non-free >> /etc/apt/sources.list.d/newrelic.list'

sudo wget -O- https://download.newrelic.com/548C16BF.gpg | sudo apt-key add -

sudo apt-get update

sudo apt-get install newrelic-sysmond

sudo nrsysmond-config --set license_key=<your_license_key>

sudo /etc/init.d/newrelic-sysmond start

You can see all your servers (with new relic installed) on your dashboard.