On the Quick Launch bar or in Site Contents, click the library to which you want to add documents.
Right-click the Start button.
Click Open Windows Explorer.
Browse to the folder that contains the files you want to move.
Select the files and drag them to the SharePoint library.
On the ribbon of your document library, click the Library tab.
In the Connect & Export group, click Open With Explorer.
Drag files to the Explorer folder.
Close the Explorer window.
Click the Refresh icon in your browser.
Have another Explorer window open prior to moving documents so that you can easily drag files to it.