On the left side under the Pages heading, select the page you wish to edit.
Based upon the page template, different editing abilities will be available. You will notice on the page a section called Page Content and word processor section.
Place your insertion point inside the white section and begin typing. User the toolbar above to make formatting changes.
Once you have finished your changes, select "Update Page" at the bottom of the Page Content section.
You may now view the live site to see the finished product.
