Here is what I do, step by step. It ends up sounding pretty good. Note that I am using version 4.26, so you are likely using a newer version than me. If so, some things may be in different places for you:
Increase the volume--usually it records much softer than you want to play it at. If you increase the volume AFTER adding in the hissing, the static becomes way too loud. I usually up the volume 200%, but it will depend on your recording.
Next, we lower the sound quality. Choose the "bandpass/bandstop" filter. Choose "bandpass" (it's the default) and make the range 300mHz to 4000mHz. Make sure you have the whole clip selected.
;D Now to add a little hiss. Open up the "dynamics" window (under the effects menu). You should see a little line graph. There should be a "preset shapes" option. Select the "hiss noise" shape. There should be a zig-zag in the middle of your line now. You don't want to use this though, because it will add WAY too much static to your sound. Place your mouse over the two white dots on the corners of the zigzag. Drag them closer to the middle of the line, until they are almost straight. Just a tiny amount will do it. Check out the attatched picture to see what I mean. Call it "radio buzz" and save this filter for later use (so all your clips have the same level of distortion), and apply it to the whole sound.
EDIT I can't attatch the image, so I've posted it here:
http://www.freewebs.com/general-barron/images/radiobuzz.jpg :-X Now you are done with Goldwave. You may want to apply more filters, but I suggest you don't. Keep in mind that you still need to convert to OGG, and that will drastically change the sound. I use dBPowerAmp music converter. NOTE: make sure you don't save files as OGG with Goldwave, or edit and save OGG files. It will mess up the conversion. Use dBPowerAmp or another music converter. Here are the settings I use to convert my radio sounds:
mono
32 kbps
12000 Hz
That gives good compression without losing too much sound quality. Note that for music files I use different settings that keep more sound quality (but make a larger file).
Hope that points you in the right direction!