How do you grab traffic to website through FB page, money free? Well, let's just say you have to invest not on money but on TIME. You have to prioritize on engagement, and that can only be achieved through having REAL fans.
Share insightful posts and attractive images that are inline with your website/products/services, and if you have REAL fans that are really interested with what you could offer, engagement can be as smooth sailing. Then on your post, you can indicate your website's url for their accessibility.