how does kodi audio mixer work?

i just've installed it but when i open the add on it just appear this.
https://udelasalleedu-my.sharepoint.com/:i:/g/personal/jna66849_udelasalle_edu_mx/EVEu0_tOSaRHnbYSJJAcMkcBskZJzMdo0_g8O3la9qfviw?e=m38tWP
 I'm running in the last version of kodi on libreELEC