Since version 6.5.2 the UpSlide Library can be hosted in a Sharepoint Online Document Library.
Once the Document Library has been created in a Sharepoint site, its path can be used directly in UpSlide Settings to set up the library for the user.
You won't be able to add in UpSlide a path to a subfolder of a Document Library.
For the moment, your Document Library path needs to have "sites" or "teams" in it. It won't work if the Library is created on the root site of SharePoint.
You will also need to grant consent to UpSlide so that it can retrieve content from SharePoint.
Create the Document Library