Building out a landing page doesn't automatically mean you'll begin getting leads immediately. Building a landing page is very much like purchasing a set of business cards... once you have it you've got to get it in front of people and only then will some of those people begin reaching out.
You've got to promote your landing page and one such way to do that is through Facebook. This video will introduce you to both posting a landing page to your Facebook Business Page and also boosting it (paid advertising).