The Site Search within Overdrive will find any files within the Site Folder you selected when setting up your site.
The Search tab allows you to give Overdrive permission to index the content of your Google Docs, Sheets and Slides. Doing this will improve the site search by showing users results including the content of these files.
Please note: indexing will store file contents on our cloud and may slow down site search.
You can also setup how you wish the Search Results page to look from this tab.