Select "Yes, our venue has Ethics Chairs and Reviewers" from the venue request form. This can be done when submitting a new support request form, or after your venue has been deployed by using the "Revision" button. This will generate an "Ethics Review Stage" button from the venue request form as well as other necessary customizations.
Recruit Ethics Chairs and Ethics Reviewers using the "Recruitment" button from the Venue Request form.
Once you have identified which papers need ethics review, create a comma-separated list of their paper numbers.
From the venue request form, run the "Ethics Review Stage". This will allow you to customize the Ethics Review form and pass in your list of papers that require review.
Now Ethics Chairs will be able to assign Ethics Reviewers to the flagged papers from their Ethics Chairs console. Ethics Reviewers will see the option to post Ethics Reviews to their assigned papers.