Sure -- just load the WAV file into WavePad, then from the FILE menu, select SAVE FILE AS, which will open a new window. At the bottom of the new window, find SAVE AS TYPE -- it will be set to "Wave (*.wav)" -- click on the dropdown arrow to the right, and select "MPEG Layer-3 (*.mp3)" -- then go to the box above and type in a new file name.
The first time you use this MP3 option, WavePad will go out to the Internet and fetch the converter it will need to work on your computer. After the first time you use the converter, it won't need to reconnect in the future.
Jerry