Here is a tutorial on how to add or edit points for an Assignment.
You can add or edit the amount of points on a given assignment.
Note: When an assignment is set as a moderated assignment, only the moderator or a Canvas admin can edit the assignment after it is published.
Open Assignments
In Course Navigation, click the Assignments link.
Edit Assignment
Click the assignment's Options icon [1] then click the Edit link [2].
Edit Points
Edit the points available for the assignment by typing in the points field.
Save Assignment
Click the Save button.