Download or purchase the audio editing application of your choice. Once downloaded, open the program.
Import your audio file into the application by dragging or choosing the "File" and then selecting "Import" from the drop-down menu.
Choose the "Normalize" option from the "Effect" menu. Leave all of the options at the default setting and select "OK." This will raise the audio to the loudest setting possible without clipping the audio.
Select "Compressor" from the "Effect" menu and then press "OK." This will even out the audio levels and prevent the highs and lows.