Insert the "Sony eBook Library" CD that accompanies your PRS-300 reader into your computer. Install the software.
Download an eBook from Sony's website or another source.
Turn on the Sony PRS-300 with the slide switch at the top of the reader. Connect the reader to your computer with the USB cable.
Open "Sony eBook Library." Click "Library" in the source view, and then "Books." Drag the books to the Reader, indicated by an icon on the toolbar at the left-hand side of the program. Do not turn off the PRS-300 while the files are transferring.
Open the "My Computer" folder on your desktop. Locate the folder for your book reader titled "READER;" double click on this folder.
Open the following folders in order: "Database," "Media," "Books." The PRS-300 stores eBooks in this folder.
Open the folder on your computer containing eBooks you would like to add to the PRS-300. Select the files and drag or copy them to the "Books" folder. Allow the computer to finish moving the files.
Unplug the reader from your computer. The reader will catalog the new books for five to 10 seconds; this is indicated by the rotating arrows and the word "loading" written at the bottom of the screen. Open and read the books you just added.