If you have a website, inform the people that you have a Facebook page by using a Facebook badge, or a Like button. Anything that can inform them that you have a Facebook page would do. I have a question, by the way. I want to make things easier for you. Why not target those who have already bought your product, just like what Ted mentioned? It's going to be a lot easier to target them, especially when you've given them great products and services.