We found a great video that a user made on Youtube (username: JosGJosG) that talks about Third Party Sensors.
JosGJosG takes you through starting up ROBOTC and going through the Preference settings in order to enable the ability to use Third Party sensors.
Description of the video (from youtube):
When ROBOTC is downloaded, it is initially set up to recognise only LEGO sensors. A set-up change has to be made to allow ROBOTC to recognise third party sensors, (HiTechnic, MindSensors, Firgelli, etc.). This video shows how to make that change, and also briefly mentions the difference in set-up between the full ROBOTC, and the simplified Natural Language ROBOTC. This video is one of a series of free video tutorials that introduce students to LEGO MindStorms NXT-G and to the use of Third Party Sensors; you can see them at www.DrGraeme.net.