Turn the can opener upside down. The can-opening blade should be facing you. The wide end of the opener should be pointed away from you.
Push your fingers onto the back cover. Grip the can opener firmly with your other hand. Push your fingers downward to remove the back cover. This exposes the batteries.
Remove the two old AA batteries from the compartment. Place the new batteries in the compartment. Position the left battery with the battery post facing downward. Position the right battery with the post facing upward.
Reattach the back cover. Push it up firmly to lock it into position.