Lay the clock down on a towel resting on a flat surface. The face of the clock should be facing the towel. The towel is to keep from scratching the face of the clock. Remove the battery from the clock.
Attach the solar cell to the battery of the clock. Attach the positive wire to the + pole of the battery and the negative wire to the -- pole of the battery. Make sure the wires are connected well. Return the battery to the clock.
Glue the cell to a side of the clock where it will not block the numbers. Just place the glue around the edge of the cell. If the clock needs more balance, glue a piece of plastic to the bottom until it stands with the cell attached.
Find a sunny spot in your house or garden. Place the clock with the solar cell in the sun and allow it to charge for a few hours. Place clock in the sun every few days for a few hours to recharge the solar cell.