With the gimbal mounted, you now need to configure it's firmware. These instructions will reference the Tarot T-2D Assembly Manual v1.1 [1], as revised by John C. Lin (3rd Party).
Make sure to start with the gimbal OFF (battery is unplugged), and your camera mounted in the gimbal.
Every time you power-up the gimbal, it goes through a calibration procedure that takes about 15 seconds. During this time, it is critical that you do not move or bump the gimbal or quadcopter, that there are no obstructions restricting the gimbal's movments, and that there is a camera in the gimbal. Check out the "LED Indicators" section of the Assembly Manual for an explanation of the status indicator lights.
For additional information on RC control of the gimbal, please see the Assembly Manual.
Links
[1] http://www.caution.se/media/Tarot_2-Axis_Brushless_Gimbal_User_Manual_V1_1_Revised_by_JCLin.pdf
[2] http://image.helipal.com/helipal-tarot-t-2d-software-v15.rar
[3] http://learn.parallax.com/sites/default/files/content/ELEV-8/Gimbal-Mount/Gimbal-Mount-02
[4] http://learn.parallax.com/sites/default/files/content/ELEV-8/Gimbal-Mount/Gimbal-Mount-03