Run MediaHuman Audio Converter application and press Add button on toolbar to add video file. Or you can use drag'n'drop for this aim.
Now you need to select MP3 as output format. To do it press the fourth button on toolbar.
You can select among predefined MP3 settings or set up your own by choosing Custom.
Now we are ready to start conversion. Press the last button on toolbar and wait while it is processing. If you change your mind press it again to stop the conversion.
It is done. You can locate the extracted audio file pressing the Locate button on video item.