Sue...if that's all you wish to do, "Super" is likely a BIG overkill for you. It does a lot, but it can be daunting...

Audacity can open those .wav files and convert (they say 'export') them to MP3. Instructions are in the help file.

There are several ways to do it. Let us know what you try and if it's working. If not, we'll try other things.