ct1

Ensure you are tapping the sensor to the face of the watch and hold it there for a second or two and the watch will register the tag. The entire circular section must be tapped squarely against the face of the watch prior to taking the shot to register and track the distance prior to hitting the ball. 

Through the watch you can manage the CT1 tags away from the course by opening Settings > Golf Settings > Club Tracking > CT-1 > Ensure the status is showing enabled on the next screen > Then tap "Manage Tags" > You can then check if the tag is assigned by pressing the tab against the screen and the watch will give you the club assignment status from there. 

This thread is a duplicate to another thread on the forums post linked here: Just bought s70 and CT1 sensors dont seem to be working at all