The Disavow Tool
The Disavow Tool is normally used when you’ve made a mistake with your SEO strategy (or an agency has), or when you’ve been the victim of negative SEO.
Negative SEO, by the way, is when a competitor builds lots of really spammy links to your website, to make it look like your building rubbish links yourself.

Google recommends that you should not use the tool however, unless you are certain that poor back-links are impacting your rankings.

Here’s the process:
1. Sign into Google Search Console

2. On the menu on the left, click Search Traffic, then Links to Your Site

3. Click “More” on the left hand side:

4. Click on “download more sample links”
Tricky part:

5. You need to create a .txt file containing the links that you want to exclude from your backlink profile

Make a list of the links from each domain.
For every different domain that you are excluding, you need to add a comment, use the # sign at the start of the line to identify it as a comment line.
For example:


#Paid for links negative SEO
http://www.jonnysBlog1985.com/sponsored-post/
http://www.jonnysBlog1985.com/sponsored-guest-post-about-cars/


To exclude a whole domain, add something like the following to your .txt file:

#Negative comment spam (ignoring the entire domain)
http://www.negative-spam-blog.com


6. Once you have created your .txt file and are happy with it, go to the Disavow Tool Page

7. Upload the .txt file

That should be it.
Ideally you should also try contact each site, and ask them to remove the links to your site, before Disavowing any.

You can evidence your attempts to contact the webmasters by saving the code of the emails in another .txt file, but from the case-studies I’ve seen, this isn’t necessary.
If they don’t reply, just Disavow them, as shown on the official blog post:

Please contact drewjohngriffiths at Gmail.com for more information about my freelance disavow service.