Cylinder Head

Just bought new cylinder head for my 1993 escort along with a torque wrench, a tap and die set, and a compression kit, along with all of the neccesary bolts and gaskets. Just have a question about the torque wrench. After i put how much pressure i want to be applied, how will i be notified that it has reached that setting. Some say that the wrench will click. I dont see how the wrench knows how much is applied and when to "Click", can anyone expalin to me? Also i am open to any suggestion on installing the head, for this is my first time.

The ones I've used will click like you say. I tried looking on a couple websites to see how they know when you've reached the desired torque...but I failed.