How do I convert a music file into an mp3 so that I can send it via email?

What file format is it in now?

It is in WAV I think. My hubby is in the music business. People ask us to send music all the time and we have someone do it for us, but we want to do it ourselves. Usually we have the music in windows media player. I know that mp3 are faster to open. I just don't know how to convert it.

The key is in what format the file is in now. If it is, indeed, wav, then there are a variety of ways to convert it:
Convert wav to mp3

If it's in another format other than .wav, then do a Google search for

Convert *** to mp3

... replacing *** with whatever the file format of the file you want to convert is.