My score is 88 bars wide !! How can I wrap it?

When I first used Muse Score a couple of years ago, on my very first score I ended up with the entire score on ONE line - it's 88 bars long (wide)!!

Obviously, this makes it useless for just about anything other than being accurate documentation of the piece. How can I turn this into a usable score with multiple lines?

I've tried adding a break - nothing happens. Perhaps I'll end up cutting and pasting to another document.

But surely there's a way to do this without resorting to an error-prone cut-n-paste job?

tia, malcolmtent.