Headphone jack configuration

I just got some new speakers for my g4 and I can't get my headphone jack selected as my primary audio output. When I open the System Preferences and go to the Audio section, the only output selection is the Built-in speakers. How can I install the headphone jack so that I can listen to music through the new speakers? The speakers are a regular audio jack and not usb. I use Mac OS X 10.4.11 with all the latest updates that I can download.

Thanks in advance.

Ya should be able to just....plug 'em in.

I did plug them in, but it still didn't work. Is as if I haven't pluged it in at all.

I think the problem is that the jack is broken. When I try to plug the cable in the microphone jack, it fits perfectly, but when I try to put it in the headphone jack it seems lose.

I saw some people complaining about the headphone cable that it was too thick to fit the jack. Maybe I need one of those thick ones to plug in to my jack? Or is it just broken?

Thanks in advance.