Here are instructions from blogkindle.com:
You can copy documents in supported formate to your Kindle following these easy steps:
- Connect your Kindle to your computer via USB cable. After drivers are installed, you can see your Kindle device as a disk drive
- Navigate to “documents” folder on your Kindle device
- Copy your files in supported format there (PDF/TXT/MOBI/PRC/AZW)
- Safely eject the device
Your documents should now be visible along with your other eBooks in the home screen.
Read more: here!