To integrate your career site on your Facebook page, you need to activate your Facebook app in Teamtailor. To use the Facebook app you need to have more than 2000 likes on your Facebook page, as well as having added a Jobs tab to the page in question. If you do not know how to do so, you can find instructions for that here, or reach out to Facebook's support.
How to activate in Teamtailor
Simply go to Settings -> Facebook app, and then choose your company's Facebook page.
In Facebook, you can edit where the Work with us button is shown.
Note! You must have permission to add apps to your Facebook Page in order to be able to do this.