Download Audacity Here

 http://audacity.sourceforge.net/download/windows

File > Open >  Select file

Determine the part that you want to cut out  Then make sure you press stop

 
After that select the part you want to cut out of the audio track  Just like selecting text
Next, click Cut  And you will notice that the part is now gone

Finally, after you're done editing go to

File > Export
And select where you want to save it  this will save it as an MP3 file

That's all =)
Electronic Teacher : Sana Al-Buraiky