You need to create a custom text box widget via your widget layouts section under the "design" menu.
Once you have the button code, press the source button, paste the code
and save it. Otherwise simply upload an image and create a hyperlink to
your pages.
For links to Facebook to work,
go to your privacy settings on your Facebook store and adjust your
sharing on facebook settings as appropriate and click into connecting on
facebook and make the settings in a way that allows people to access
your site. As Facebook is regularly changing
this, you'll just need to play around with this until the settings are
such that ALL people can see your Facebook site, not just people logged
into Facebook.
