Step 5: Add the Power Source
Strip the ends of the wires and wrap the bare wire and a small bit of aluminum foil together into a ball.
(I call myself a photographer, but I obviously need to work on my depth-of-field and flash diffusion skills.)
Use the electrical tape to hold the batteries together in series (postive terminal to negative terminal) and the wire ends in place on each end of the battery stack.
Polarity is important here. Test the light at this point and try reversing the connections if it does not work. (Remember that you have to push the switch while testing.)
Wrap a second piece of tape around the terminal ends. Stretch and wrap the tape tightly, insuring a postive connection.
Fit the battery pack into the end of the finished pen.