What is the easiest way to upload multiple files to a Microsoft SharePoint site?
If you are using SharePoint 2013 and Internet Explorer 10, then you can actually click and drag files to the folder.
Here are the steps to follow:
Open the SharePoint site.
Open the appropriate Folder.
Open Internet Explorer on your desktop.
Select the appropriate files.
Click and drag to the area above the files as seen below:
If you do not see the "drag files here," then you are either not using SharePoint 2013, or you are not using Internet Explorer 10. If you are in an older version of SharePoint, then click on Documents and an arrow next to Upload Documents. If you click on that arrow, then you should have the option for Upload Multiple Documents, as shown below: