You've got to understand that marketing has got nothing to do with SEO, or Facebook, or Twitter.
Marketing is to do with understanding your product, knowing what part of the market it will appeal to, and being able to communicate the benefits of the product to that market. Until you get that right, all the Facebook pages and SEO techniques in the world are not going to help.
I have to agree with the advice given by Ultimate and Ted S. You've been hired as a marketing executive, but you admit that you don't know how to go about marketing. I'd suggest you start by having an honest discussion with your employers about your abilities, and how you can best use them to meet the company's goals.