We can create an <a> anchor hyperlink which will share a specific URL on Facebook.

http://www.facebook.com/sharer/sharer.php?u=<url>

For example, the following URL which share my About page on Facebook.
http://www.facebook.com/sharer/sharer.php?u=https://eureka.ykyuen.info/about

Done =)

Reference: Creating “Share This on Facebook/Twitter” Links