how to install tacomethrus in Cavalier 96 2.4L

Hi, I have a 1996 Chevy Cavalier with a 2.4L engine, and it didn't come with a tachometer from the factory. The thing is, I want to install one, but I don't know where to get the signal from. Can anyone help me? From what I've heard, the signal can be taken from the crankshaft negative terminal, but I don't know where it is or what it is. Thanks in advance.