does anyone know how to use chordica music program

iOS and iPadOS

Hello listers, I found on this site recommendation for a music application chordica. I downloaded the lite version. The reviewere wrote that the application is accessible, however, I don't find it accessible at all. After you open the app, there are many buttons and there is no explanation what they are for, when you double tap on them nothing seems to happened. Does anyone has more luck with this app? Many thanks. Zdenek