This page tells you how to set up Windows audio so you can use the EarthLink Conference Manager. Getting your microphone and speakers adjusted must be accomplished via the normal windows audio control panels (or whatever control panels came with your audio card.)
Here are some settings to look for in the volume control (assuming you want to talk into the microphone and listen through your speakers.):
Note that the microphone is muted. This is okay, since this is usually the device that routes your microphone directly to your speakers, which you don't want, since it can cause loud, screeching feedback.
Next, select Options|Properties, you'll get a dialog box that looks like this:
Select the recording item as shown above and click OK.
You should get a display that looks like this:
Try selecting the items as shown above. Also adjust the microphone to a level that seems reasonable for your setup. You can use the Windows Sound Recorder to check this, or you can just create a session in Conference Manager with audio and and adjust it on the fly. Under the Advanced button there may be a setting that allows Automatic Gain Control on the microphone. Sometimes enabling this option (if present) can improve the quality of the audio input.
As mentioned above, this is the generic Windows way of adjusting the input/output audio devices. Many audio boards come with their own mixer applications (which may override the Windows mixer.) The same general ideas apply for those other mixer applications.
There are a variety of things that can go wrong with your audio setup. Unfortunately, there are so many that they can't all be listed, but here are a few things: