While editing a page you will see the Divi Builder. From here you can edit content within the grey boxes by clicking the menu icon for that box (looks like three horizontal lines). Once you are finished making changes to a box, click Save & Exit. When you are finished making changes to a page, click the blue Update button to the right of the page. (NOTE: If you do not wish to keep changes, simply navigate away from this page without clicking update. A box will appear asking you to confirm you wish to leave.)
If a box is green, that means it is a global module. Changes made to a green module will take effect on every page it appears.
There are various types of modules (grey boxes), including: text, image, and call to action. Each will have different content fields you can edit. For more details on using the Divi Builder, please visit: http://www.elegantthemes.com/gallery/divi/documentation/
