Step1: type 'roscore' in a terminal.
Step2: open a new terminal and type 'roslaunch turtlebot_gazebo turtlebot_world.launch'.
Step3: enter the directory where the file 'interface.py' is, and run it. (You can change the variable 'speed' and 'steer' in the python file, otherwise the turtlebot won't move.)
Write some codes between 'input' and 'output', to realize some function.
overwrite the file 'openni.launch' in '/opt/ros/kinetic/share/openni/launch/openni.launch'.