Most of our emails in Pardot include images/graphics such as a banner at the top of the email, section breaks, or video stills. In order to be able to include an image in a Pardot email, go to the "Content" tab in the top navigation bar and then "Files" in the navigation bar to the left.

From there, you can either click on "+ Upload Files" and select one from your computer, or if you've downloaded the image/graphic, you can just drop the file into the grey space. 

When you're in an email, click on the picture emoji in Content Editor to the left of "Merge Field" in order to add an image into the email. You can get into Content Editor by clicking within the email in the section you'd like to add an image to. 

Once you click on the Image icon, click into "Custom URL" under "Image" to select the image that you added in Files. Then, click OK and the image will be added.