I downloaded the Linux sound driver for my onboard audio and I looked through the howto directory and I don't see anything on getting sound up and running except for a soundblaster doc.
I did everything in the sound driver README but I'm lost as what to do next.

Dunno what your where you got your drivers from, but I recommend the alsa project [1], they support a very large number of sound devices and have some good documentation on their site.

[1]http://www.alsa-project.org

If you provide more details on the steps you've tried, type of hardware, the actual driver you downloaded; it would probably actually give you better responses from members here. Until then, were just as clueless as you are without details or more information.

All you have to do is load the sound modules using modprobe. If you've got a PCI/PNP motherboard you don't have to bother with irqs or io ports, Linux will handle that by itself.

If you're on a redhat variant you can use sndconfig to help you, but in general it's not necessary.

What kind of sound device do you have? Chances are your distro came with a driver already and you didn't need to download anything.

Something else you may want to look into: not all distros allow regular users to play sound by default. You may need to give yourself access to /dev/dsp. You should also check that the volume level isn't set at 0. It sounds trivial, but you'd be amazed at how many competent computer users spend days trying to fix a sound problem then find it was just muted.

The error is that it says there's no device that /dev/dsp relates to.

I looked back at my manual and found out I downloaded the wrong driver so I went back to the manufacturer's website (realtek.com.tw) and downloaded the drivers. They are actually alsa.
I configured, maked, and make installed the drivers and then I executed snddevices to make the sound devices.
The last step is to edit the /etc/modules.conf. The only problem is slackware 9 does not appear to use this file...

Your looking for /etc/rc.d/rc.modules most likely.