Rel Canonical

How to fix them on word press I'm new at this but I don't get the whole Rel Canonical stuff.

How do you mean fix them? Are you already using the tags and they are incorrect, or some other issue?

Canonical tag is simple, if you have two pages with the same content, you add the canonical tag to duplicate pages pointing back to the canonical 'main page'

http://googlewebmastercentral.blogspot.com/2009/02/specify-your-canonical.html