If you have already submitted your assessment and it is not yet closed, you can still edit it.
To do so, navigate to the 'Reviews' tab > 'Your assessments' > 'Completed.' Here, you'll find the reviews you've completed of yourself and other people. Click into the assessment you wish to edit.
When you've reached the page shown in the screenshot below, click on the 'Edit' button in the bottom right-hand corner.
Please note: editing is no longer possible after the review cycle has closed.