Is this a Kindle book or a PDF file? If it's a Kindle book, do you have the Kindle application on your PC? See: http://www.amazon.com/gp/kindle/pc/download -- probably you can share it that way, but I've never tried it myself. If it's a PDF, you can transfer it to yourself using any of the common methods, such as: attaching it to an email and sending it to yourself, or using a cloud storage account that both your Fire and your PC have access to. If that doesn't help, please check with Amazon.