Go to Verisart Shopify app and select 'Settings' tab
Scroll down to the Certificates section, find the 'COA customizations' panel and click 'Manage'
Choose your logo, background and subheading
Logo: 50px x 300 px (.png or .jpg, under 30MB)
Background: 900px x 1500px (.png or .jpg under 30MB)
Hit save! All your certificates will now be issued with a customization