Navigate to settings and scroll down to find the default background settings for postcards and notecards.

Images uploaded here will be set automatically for any order submitted to this account/sub-account unless a different background image is specified.

File Upload

Using the controls, upload your custom background browsing for the file you designed elsewhere or in Canva. 

To clear a design, click on the red 'Clear Image' button.

Be sure to save any changes before leaving the page.