Found under Sections -> Add Section -> Feature Image:
Full Width - Enables you to achieve Full width that covers in both LEFT and RIGHT padding.
Image - Where you will attach the image
Section Style - Allows you to add different section layouts
Link - The image/banner would be clickable depending on the link you attached.
The image/banner varies depending on the dimensions you upload, basically it would display accordingly as per your dimensions. If you want a much more smaller banner then upload something like 1200*480 or 1200*600