You can find this section under Email Marketing > Email Common Content in the IRP Marketing Cloud left navigation menu.
Email Common Content allows merchants to create commonly used email content that can easily be added to templates. It’s a very efficient and time saving way to create headers, footers, banners and other common content merchants frequently add to their emails.
Common content is created in a single row and does not support complex multiple row layouts. Merchants can create as many individual row common content as needed to support complex layouts.
Applying Common Content Rows
Common Content Rows can be added directly to an email template in the same way as Empty rows.
In the Content Editor just select the common content type from the Rows dropdown and drag the content snippet directly into the email.
NOTE: When editing content it is important to 'Insert' the content after the editor has closed when the following message is displayed.. 'Changes have been made to the content. Please ensure the content is inserted.'