HP LaserJet 5 printer

I'm not sure if this is the place to get info, but I just bought a uswd LaserJet 5 printer and am trying to connect it to my Dell Dimension 2400 desktop. Currently an HP OfficeJet 4315 is connected and workinf and I'd like to lewave it hooked up. The guy I bought the LaserJet from said something about configuring it as a default printer. I'm a moron on computers and would appreciate guidance without all the hitech computer jargon ( basically I need info like plug in square socket to blue port or something simple like that. Is this really complicated to do? The laserjet did not come with any software, only a power cable and a serial connecter that I found a socket on the back of my Dell that it connected to. Can anyone give me easy to follow directions? JBK