To add a new file to the Media Library, click on the Add New link in the left hand navigation menu or the Add New button at the top of the page. You will be presented with a page similar to the popup window that is displayed when uploading a new image in your Post or Page. To upload a new file to the Media Library, simply drag your images from wherever they are on your computer, into the area marked Drop files here. Your file(s) will be automatically uploaded. Alternatively, click the Select Files button and then select the files that you’d like to upload, using the dialog window that is displayed. Once your images or files are uploaded, they’re listed below the file uploader. If you’d like to edit the file properties, click the Edit link next to the file.
To view a file, hover the cursor over the particular row that contains the file name and click the View link. If the file is an image, you'll see a larger version of the image. If the file was another type of file such as a text file or PDF for example, you'll simply see a link to that file. Click the link to view the file.