Opening the Staff Properties dialog

[control] click?

"Logically" it's right click, but of course many of us don't use mice ot touchpads with physical buttons to click, and the mice on most Mac don't have a right button anyhow. Every computer is set up a bit differently in terms of what gesture will produce the "logical" effect of a right click, but it should be the same across all applications on your computer. If there is no physical right button to click, Ctrl+click might do it, or perhaps two finger tap. Consult the documentation for your computer / OS if neither of those seems to be the right click gesture.

Ian, if you go up to the top left of the screen and click the Apple menu, you'll be able to open System Preferences. The Mouse section of the preferences should allow to you to configure a right-click—what the settings will look like may depend on what type of mouse you have plugged in, but with the Apple Mighty Mouse, it's just a matter of setting the the right-hand button to "Secondary" rather than "Primary."