We download it from HERE, We install and run it:

The first thing to do is to update it, To do this, click on “Update Plugins”,

Click on “Update” and follow the update wizard.

Once you have everything updated, Let's perform the scan, for this “New Scan Task” and on the right side we put the host to scan, can be an IP, a PC name or just a DNS name. Click on “Next”,

We select what type of scan we will do, I recommend making a custom one (The 3rd option) but for the example I'll use the most aggressive one. Select the one that interests you and click on “Scan now” Getting Started!

Scan process takes a while…

And at the end it gives us a report in html format so that we can deliver it to the client where we are doing the audit or see the results.

Official Website: http://www.tenablesecurity.com/products/newt.shtml or HTTP://www.nessus.org