A file can be almost anything [see supported filetypes for a detailed description]; the Media section of WordPress is where it is stored and accessed.
To upload a file, hover on the Media section in the nav bar on the left side and click on the Add New link, which will take you to the Upload New Media screen. You’ll see a box where you can upload media by clicking the Select Files button. A file window will show up where you can select one or more files. Once selected, click the Open button. That’s it! WordPress will start uploading your selected media. If there are any issues, WP will let you know with a meaningful error message.
[If you have any questions or issues, copy the error message and send it to the Help Desk, requesting a ticket be opened to the Web Team, subject ‘WP File Upload Error Question’]
You can see what the uploaded media has for settings in the library by clicking on the Show link to the right of each piece of uploaded media.