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).
Simply go to Content -> 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 to do this.