Newby question

So I must be a dunce but I am totally lost. I just downloaded the latest version of audacity the normal one I believe not the smaller version to our 2008 mac which is still running strong. I get all my music from Itunes as well. With that out of the way why is that after I hit the play button and listen to the mix I’ve made I can no longer do anything I hit play and then re select my song and I can’t make any changes nor save the remix. What am I doing wrong?

Press the square stop button to stop playback (not the || pause button).

literally a life saver