Audacity

Audacity is an easy-to-use, multi-track audio editor and recorder for Windows, macOS, GNU/Linux and other operating systems. Audacity is free, open source software.

download: https://www.audacityteam.org/download/ 

getting started: 


more help: https://support.audacityteam.org/ 

Beware! Using Audacity to edit your source files is DESTRUCTIVE meaning any adjustments made to your file are permanent. Therefor, good practise is to work in a copy of your original file.