Put the picture or name into the jar. Say a rhyme or chant that indicates your intent and what you want this to accomplish. Close the jar and bury it where it won't be disturbed. Or you can do it the old-fashioned easy way. Make sure you include what you want to happen.
Same warning applies.
Normally I don't post any type of spells on a newsgroup, but I'm making an exception in your case. If you're stupid enough to do this for the wrong reasons, then you deserve what you get. If clothing is used, cut or tear it into tiny pieces. Mold the wax and cloth, or hair, into an image of the person to whom malice is intended. The ritual is repeated each evening for three evenings in a row.