Create panel > Helpers > VRML97 > Object Type rollout > TouchSensor
The TouchSensor helper lets you set up an object so that selecting it in a VRML97 browser starts a set of objects animating.

The Touch Sensor rollout contains the following options:
Pick Trigger Object—Specifies the geometry that will be the trigger for this TouchSensor. Click this button, then select the geometry.
Enable—Activates the Touch Sensor. When this box is turned off, the sensor has no effect, even if objects have been selected.
Pick Action Objects—Specifies the objects in the scene to control with this helper.
Delete—Deletes an object from the list of picked objects.
Icon Size—Determines the size of the Touch Sensor helper in the scene.