EC1 - This container is reserved for the main (large) image in the MEGA Banner sequences.
EC2 - This container is available for your text or image content, and is integrated into your MEGA banner code sequences.
Here's screenshot of the EC2 sidebar code used for the homepage of this O Mega site. The pink highlighted code areas means the formatting has been removed for the code only. And for the main area, some space was created, the text was customized, then formatted to align right (from RapidWeaver's "Format" option in the main top toolbar).
EC3 - This container is available for your text or image content, and renders below both the main content and sidebar containers.
If you're new to using Extra Content, click here to learn more