How to properly add an activating zone that triggers something?

[Anbeegod]

I'm adding an activating zone to a place. As the player enters the zone, they would be teleported to somewhere else.

 

To do this, I've dragged a new activator to the cell editing window to the desiring place, however, the activator is invisible and there's nothing I could do with it.

 

I googled it and found that I should first select an object and click the activator button on the toolbar. However, I found no activator button in the toolbar.

 

 

I know how to deal with the script causing the teleporting action, but the activator issue is the obstacle here.

[prinyo]

It is the "T in a box". On hover it will show Create trigger

 

 

 

The first button after the red one (the navmesh)