To install the application run the file FreeMusepackToMP3ConverterSetup.exe.
Press the "Next" button in the first screen.
Afterwards, select the directory where the application will be installed, or simply accept the default one and press the "Next" button.
After the application is installed you can start it by clicking the Free Musepack To MP3 Converter shortcut icon on the desktop or by selecting the Free Musepack To MP3 Converter shortcut from the Windows start menu.