Do you want to completely remove the header of your site? Some CSS tweaks in Canvas can help you how to do it. Please refer below
Canvas Child theme
Step 1 Login to WordPress control panel
Step 2 Provided that you have already uploaded a Canvas Child folder containing style.css and functions.php files in the themes folder using FTP. Go to Appearance > Editor
Step 3 Enter the following codes in Canvas Child style.css file.
Theme Name: Canvas Child
Description: Child theme for the Canvas theme
Author URI: http://www.jezweb.com.au/
note: We are using a Canvas child theme so that your CSS settings will not be changed if there is an update with the main canvas theme.
Step 4 Click Update File and go to your online site. You should no longer see the header on your page.