Changing Mark of Entire Assessment
Go to Teaching, then Courses. Go to the course that has your desired assessment.
Go to the Users & Groups tab and click Details beside the learner you wish to update.
Click on Details next to the assessment you would like to edit. Go to the attempt and click on the existing assessment result.
Enter the new grade of the users assessment. Press Ok.
Changing Marks of Individual Questions
If you click on Results for Attempt instead of editing the overall grade, you will be able to edit the marks of individual questions.
On the next page, you will see this. On it will be some of the learner's information, as well as a drop-down menu, a graphical display of the questions, a mark adjustment field, and a button that says Switch to grading mode/I'm finished grading. If you see Switch to grading mode, click that first.
To change the mark of a question, simply select the question number. You can then use the Update score field to mark the question. Don't forget to hit Update when you are finished! Once you're done, simply click I'm finished grading at the top.
You will now see a notification that says This assessment has been graded. The user may view their assessment score. If you want to leave any feedback, now's the time to do it! You can leave overall feedback using the field at the bottom, or question-specific feedback by selecting the question number. If you have other learners who you would like to edit, you can use the drop-down menu to select them.