Hi, thanks Mary.
I'd never find my way back to the section I was reading now.
In the meantime, I read the end of the document you linked me to, and realised I was trying to do exactly what it warns against...
But in the mean time, I took a deep breath, though about what I was doing, and found my way to the COURSE settings.
Because I'd added the teacher manually - he'd never enrolled in a Course. Once I enrolled him I could then specify his 'role' - nonediting teaher.
Thank you for your answering post, as it did help me understand and remind me what is supposed to happen.