Customizing OpenReview review form: how to add a conditional field? (appearing only if the reviewer answered "yes" to a previous question)

I use OpenReview for a conference and I need to customize the review form. I added two fields about ethics on a review form in OpenReview: the field Needs Ethics Review and the field Ethical Concerns field. The field Needs Ethics Review is a yes/no radio box:

I want the field Ethical Concerns field to appear only if the reviewer answered "yes" to the field Needs Ethics Review. How can I do so?