I haven't downloaded it yet, so I don't know. Have you tried

- the normal Help in the Apple menu bar?

- typing: System.OpenFile Help.Text and "middle-clicking" on System.OpenFile?

- typing: System.Help and "middle-clicking" on System.Help?

I don't know how familiar you are with the Oberon system. The machines had a three-button mouse and you executed commands by middle-clicking. On the Mac that's usually emulated by ctrl+left-click or option+left-click or command+left-click.

A command is: ModuleName.ProcedureName written anywhere, for example, the menu bars are really just normal text boxes that can be edited like any other text box.

For those who are interested in using the system, get a copy (either physically from a library or search for one of the PDFs scattered around the net) for Martin Reiser's 1991 book "The Oberon System: User Guide and Programmer's Manual". It describes a version of the system which is quite similar.