In the email editor, click on the "Content" tab. Click and drag an Image area into a Row.
Drop your image directly into the new content box, or select Browse in the new image area. In the File Manager, click on the My Files folder. Click upload to add your own image.*
Select the image you want to insert.
Presto! It will be added to the new image area in the template.
* Note - You'll only be able to upload images into the My Files folder
If there is an existing image in the piece that you're looking to replace, click on the existing image, then look for the Change Image button on the right-hand side as pictured here, then go through the image selection process steps above:
Check out our image upload troubleshooting article here: Why can't I upload my image?