The short answer - start with LinkedIn
If you want to use online advertising to become visible to new employees, then LinkedIn is phenomenally good. Although Facebook owns more of the traffic, LinkedIn is the professional social media, where people interact to a much greater extent with job postings than on Facebook.
LinkedIn gives you some great targeting options based on geographic location, age, education, experience and more, so you can target your advertising incredibly specifically.
Contact us to hear more about advertising with LinkedIn.