How can I remove the app from a site?
If you no longer need an app on your site, you can remove it by going to the Site Contents page.
Note: to remove an app, you must have Full Control permissions (e.g., Site Owner) for a SharePoint site.
1. Go to Site Contents
2. Remove JungleDocs 365 ( and any other apps added to this site)
3. Now you will be able to delete your site