By default, the turtlebot hydro software is configured to work with the Kinect. If you have an asus xtion pro and it has not been configured to work for you by your distributor, then you'll need to follow the instructions below.
Actually, the turtlebot software will still work without these instructions. These merely update the robot descriptions to correctly show the asus sensor in rviz and gazebo.
The instructions differ depending on whether you have a prepared usb derived release, from debs, or from source.
Live USB Installation
This is pending information/testing of the live usb release.
Export the following variable before you source setup.bash.
> export TURTLEBOT_3D_SENSOR=asus_xtion_pro
Putting it in ~/.bashrc or appended to your own workspace's setup.sh are good candidates for convenience.
> echo "export TURTLEBOT_3D_SENSOR=asus_xtion_pro" >> ~/turtlebot/devel/setup.sh > source ~/turtlebot/devel/setup.bash
Note: you can see exactly how this is working in turtlebot_bringup/launch/minimal.launch.