1. Navigate to the Quiz
2. Click on Moderate This Quiz (located on the right side under "Related Items")
3. Search for the student in the search bar. Once you've found the student, click on the pencil icon to edit and add the attempt.
4. Add any number of attempts you want to give to that student. Check the box "Manually unlock the quiz for the next attempt", if your quiz is locked due to access date/time. Click Save.
5. Now you can see that under "Attempt Left" category for the specify student, the number has changed from 0 to the number you'd inputted.