by Francois Evans.
Hi Steve,
For the Activity settings which you mention, simply turn editing on in the Course concerned, and then click the 'edit' (hand with a pencil) icon next to the Assignment activity concerned. The Grading section on the page that then appears, allows you to select a grade scale, grading method and grade category as appropriate.
Are you proposing to use a grading scale that you have already made, or do you need to use a new grading scale? Alternatively, perhaps you need to impose a way in which a current scale is used.
To set up a new grading scale, go to:
Settings>Site administration>Grades>Scales
...and then click on the 'Add a new scale' button.
Hope this helps.