Trackbacks are a way to notify legacy blog systems that you’ve linked to them. If you link other WordPress blogs they’ll be notified automatically using pingbacks, no other action necessary.
Think of trackbacks as the equivalent of acknowledgements and references at the end of an academic paper or chapter in a text book.
The instructions from this guide are referring to the WP Admin dashboard. You can get to this dashboard by adding /wp-admin to the end of your site’s url (e.g.: example.wordpress.com/wp-admin)
To send a trackback, add the trackback URI from the other blog post to the Send Trackbacks module in your blog post before you publish it. A trackback URI from a WordPress blog will end with /trackback/.
How do I send a Trackback
Go to the post on the other person’s blog and look for the ‘Trackback URI’ or similar.
Once you have that link you need to copy the URL of the link.
In Firefox, Right-click on the link and Copy Link Location.
In Internet Explorer, Right-click on the link and Copy Shortcut.
Back on your blog, scroll down from the editor to the Trackbacks module and paste the URL into that box. If the blog where it was copied from is a WordPress blog, the URL will end with /trackback/.
Publish your post and the trackback will be sent. Please note that your trackback might be sent but the receiving site may choose not to display it.