In the Admin Menu, click on the Content link.
From the Content list, click the Media tab.
Click the Add Media button.
You'll be redirected to a page of links to different media types.
Click the Image link.
On the Add File form:
Name field = enter the name of the file
File upload field = browse to and upload the file of your choice
Description field = add descriptive/summary text about the file
Click the Save button.
The completed record for the File upload will appear.
Go to Admin Menu > Content and then click on the Media tab.
The newly uploaded file will appear in the media list.