WordPress Canvas now supports customizations through the use of child themes. You can grab a blank child theme for this theme from your package folder you downloaded.
Why use a Child Theme?
If you modify an existing theme and it is updated, your changes will be lost. With a child theme, you can update the parent theme (which might be important for security or functionality) and still keep your changes.
It can speed up development time.
It’s a great way to get started if you are just learning WordPress theme development.