To upload a file(s), click the New button and from the dropdown, select Upload File(s).
In the dialog that opens, select the files to be uploaded. Click Open and the file(s) are uploaded. If you select large amount of files, progress can be viewed in the progress area to the left under your SharePoint Office 365 Site library.
Drag and drop is also supported. Selecting files from your desktop and dragging them in to the browser windows also uploads files.
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