You can define and manage reusable content with the Reusable Content list located in the top-level site of any site collection that offers the publishing features. You can insert reusable content into a publishing page as follows:
Select the Insert tab from the Editing Tools ribbon
Select the Reusable Content you want to add from the Reusable Content ribbon button
You can access the Reusable Content list by selecting More Choices from the ribbon. This displays a popup that shows all defined reusable content. From this popup, you can open the list itself and create additional content.