Selecting the "Add/Update Source Text" option from the options menus located on the Source Tool main page takes you to a page with an editing window that you can use to add to or update text from your source. Use this feature to save a passage or quote from the text for easy reference when working on your project.
Select and copy text from your source, then paste it into the editing box. When you are finished, click the "Save Source Content" button at the bottom of the page. Follow these same steps to update this source text.