Usually you can pull the eraser off and add more lead that way. Sometimes you have to feed it in from the tip of the pencil, if the eraser won't come off. To do this, just click the pencil, hold it clicked, and slide a piece of lead into the tip.

Hold down the clicker! Why didn't I think of that. I knew there was a trick. Thanks.

sometimes you have to insert the lead into the tip and press the lead in on a hard surface so it "clicks" into the holder/advancer,do this gently