Assuming you are referring to the Rat Zapper Classic:
To load your Rat Zapper, first make sure it is turned off. Then, open the lid and insert four AA batteries into the battery compartment. Next, place a rat trap cartridge into the chamber, making sure the metal prongs on the bottom are properly aligned with the holes in the chamber. Finally, close the lid and turn on your Rat Zapper. That's it! Your device is now ready to catch some rats!