Let's say that you want to share your job on your corporate Twitter page. Open the job that you want to share. Go to the Publish tab in the grey horizontal menu, create a trackable link:

https://s3-us-west-2.amazonaws.com/secure.notion-static.com/9036b2f6-9dea-4256-9dd0-3cf4ab57dcc9/01.gif

Share this particular link on Twitter. Candidates who came from this link will have the Source that you've chosen:

https://s3-us-west-2.amazonaws.com/secure.notion-static.com/19cd1c2c-1b34-490d-9390-843eb007d3ed/02.png