Songbook on Imac

Hello I have been using the Muse Score songbook app on my iMac for a long time. Last week when I attempted to transfer some scores from my desktop to my iMac and open them in the Songbook app. Everything was different in the user interface and I could not figure out how to find my songbook scores. I have a pretty extensive library of scores that I use regularly with the songbook app. How can I regain access to my songbook library?

Thank you.