You can add an image to your form using the Add Image field which is found on the Drag & Drop field section at the left side of the form builder page, click on the Media & Structure section, then select or drag & drop the Add Image field
Delete the default image link and paste your image link in the Image URL field. Click the placement field to change the position of the image (Center, Left, Right) then click the Save button. If you paste in a valid URL, your image will be displayed immediately the Image URL is added.
You can also add an image to your form using the Description field