This tutoral shows you how you can use Blender to import a free model and use it to replace the robot provided in the sample projects.
It’s also the first part in a “Simple Shooter” tutorial series. Part 2 is here. https://www.youtube.com/watch?v=XoYVb8Q42Ec
Hope it helps!
This is the model I used: http://www.turbosquid.com/3d-models/free-ready-games-3d-model/568855
Important: Please always note the license agreements associated with free resources.