Adjusting Frames in Engrave mode

The Help section says:
“In Engrave mode, you can see and adjust frames according to your needs.”
I can see the frames, but I can’t work out how to adjust them. In the music I’m inputting the Title, Lyricist and Composer details each have two lines of text which don’t fit into the frames.
I’m sure it’s a simple operation, but …

In engrave mode, at the top of the left panel is a switch which enables frame editing.

Thanks very much