Fatal error message on installation

Hi,
I just tried to install Canvas on my WP site
https://jewelrymakingfundamentals.com

I downloaded it and used the WP theme installer to select Canvas and to activate theme. When I clicked on the site name to look a it I get this message:

fatal error: Call to undefined function headway_get_page_leafs() in /home3/jewelsg4/public_html/wp-content/plugins/headway-photo-gallery-leaf/plugin.php on line 55

I had Headway theme in place, was I supposed to delete it first? How do I fix it so I can use Canvas. I am not a techie.

Thanks,
Karen Kuntz