Signals & Track What Is Going On With Signaling Mode?

Hi,
I just wanted to build a signal but I can not place the little arrow on the track, it just won't do anything. What am I doing wrong?

Thanks to everyone

 

You have to go into the attach linkable objects to track mode on the left side. (4 above the signal mode). But one small advice from me, do the signals at the very end when you are 100% sure you dont need to change anything with the track network anymore. Because everytime you change something in the track network you need to reconfigure the whole signalling system again.

 

Thanks! I am only starting to place signals experimentally in places where tracks are final