Do not continue unless you have installed Mission Planner and agreed to instal the USB Drivers during the Mission Planner Install.
Instruction for installing Mission Planner are here
If you have your Fixhawk already connected to your PC or Laptop, please disconnect it.
If you have Mission Planner running on your PC or Laptop please shut Mission Planner down
Connect the USB cable from your PC to the Fixhawk, wait until the USB connection is recognized and connected by your PC or Laptop.
Make sure no error messages displayed stating that there is something wrong with your USB connection, if there are deal with the USB errors on your PC first before continuing.
Run Mission Planner.
Follow the instructions in the video below.
To view the video Full Screen click the dual arrow icon, bottom right.