Ok so I didn't find much info on this online and when I emailed Digital Ocean, they wern't much help so I though I'd post how I did to help anyone who might be in the same situtation.
Ability = beginer
PATH = This is the location of where you need to go
$ = Code you should type, minus the $, like this,
1) Set-up a Newrelic account here
2) SSH/SFTP into your app, info on how to do that here
$npm install newrelic at the root directory
This means the location you are alreday in, you can check where you are by typing
4) Navigate to the following location PATH:
/var/www/ghost/core and open "server.js"
on this first line add
$require('newrelic'); you can add a comment above it to explain it by typing "//your comment"
Save the file
5) Go to PATH:
and copy the file named "newrelic.js" to your desktop. Open it up in your text editor and add your service key. This is the long number on your account page. You may have to click on "Reveal Key" paste the key as shown below, obviously I have screened mine out.
Now move this to your app in the following PATH:
6) Using SSH type
$service ghost restart
and hit enter, this will re-boot your blog, don't worry you wont lose anything.
7) Then go back to New Relic, log-in to your account and click the "Connect to your application" and it should work. Be paitent as it can take a few minitues to work. Failing that, email the Newrelic support people, they are super helpful! "support" at newrelic dot com
Lastly... make sure you install the iOS app if you can to allways keep an eye on your blog!
and if none of this makes sence there is a guide on New Relic.