copy the relevant template from wppizza/templates/ to your theme directory (or as of version 2.8.9.7 child theme directory if used) and edit those, so you don’t loose your edits when the plugin gets updated. Make sure to read the comments in the relevant files.
Preferably though – if at all possible – I would suggest to use css and/or some of the action hooks provided to be able to take advantage of any possible future updates or improvements of those templates