Below are instructions on how to add a file to your websites. These files can be linked to within posts and widgets via the Media Browser in the text editor.  

Navigate to the Control Panel
Click Site Content
Click on Add and then Files

Upon clicking Files, a file upload screen will appear.
Drag & drop your file in the box or click the Select files to Add button

After uploading your file, your new file will appear as the first in the list.