Follow the below steps.
Step 1: Go to the Registration Template and click on Open Block on the right menu.
Step 2: Now select “1 Column” and drag it into the canva designer.
Step 3: Now select “Image” and drag it into the previously inserted column.
Step 4: Upload the image and click on “Add image”
Step 4: After adding the banner, click on the Save button. and publish.