Whilst in a play, press the Frame Label - by default named Frame #1, 2, etc. - to access the Frame Details window.
From the Frame Details window, you can change the Frame Label (now Pass + cut in the example below) and the Frame Notes below. Once happy with the text, press Save in the top right corner. If you'd like to cancel the changes, press Cancel in the top left corner.
When you finish working on the play, you'll now see the Frame Label and Frame Notes in the play view