See How do I grade assessment submissions by student? or How do I grade assessment submissions by question? for comprehensive information about grading with the Tests & Quizzes tool.
Select the Tests & Quizzes tool from the Tool Menu of your site.
Open Actions > Scores associated with the assessment you would like to grade.
Tip: Alternatively, click the number in the Submitted column to go to the student submissions for an assessment.
In the Total Scores tab, click the name of a student that has submitted to the assessment.
The points will be added automatically based on your rating selections. The points earned will appear below the rubric in the Total area.
Click Update.