While there are many different ways to accomplish that, they all require some software. Since you didn't mention what you have to work with, operating system, other programs, etc., I can't offer a lot.
Just that I use Goldwave and Nero for this. Another possibility is converting to WM files, if you have windows media player 9 or later.
i need some help to compress some .wav files that i recorder can i convert it to mp3 please help me.