Below, COM is top center pin, NO is lower right pin, NC is lower left pin
Notice that the same symbol for the relay contacts shown on schematic is conveniently imprinted in the plastic. The COM to NC is shown as being shorted, which is the condition when the relay is off.
Usually the COM and NO terminals would be used to switch the load (doorbell).
Try drawing a circuit or describe how you plan to make connections to the relay contacts, battery and doorbell.