First of all you need a installation image (ISO file) which you can download from www.debian.org. I recommend the small network install image. After downloading the file, copy it to a blank CD, DVD or USB memory-stick. For information on creating a bootable USB memory stick, see the article “Create a Bootable Live USB Thumb Drive or Rescue Drive Using UNetbootin.” If you’re installing to a virtualbox you’re ready to continue to the next step. However, if you’re installing directly to your hard drive as a native installation, you should connect to the the Internet using an Ethernet cable since not all Wi-Fi cards are supported. For example, I have a Intel Wi-Fi card for which there are no drivers included in the Debian installation media, so they need to be downloaded manually later.