Under the Results tab there is an option for Manual Grading. Hit this and you will be told how many essay questions need grading. Click on the question you want to grade and then you will see the list of learners with an option to grade each.
Hope this is what you wanted
How is this done?
Gerald - it sounds as though you have added the Essay Questions but not created a Quiz activity.
To confirm this perhaps you could tell me if any of your learners have actually answered the essay questions yet.
Thanks Irmgard you beat me to it
I hope that sorts things out Gerald