To edit grades in a Course
STEP 1: Click the Grades link in the NAVIGATION pane.
STEP 2: Clicking on View tab lists out the users’ list.
STEP 3: Navigate the grade book to find the student and assignment score you wish to edit. Click on Override checkbox which enables the edit mode in all fields. Now, move to the Grade cell to edit the grade.
STEP 4: Select the Grade Item in the drop-down list given above the table.
STEP 5: Edit the Grade value. To save the grade, click Save button.