Click the Instagram Account field. The system loads the profiles linked to your Pages and Business Managers (including client profiles). If yours still doesn't appear, type at least 2 characters of the @ handle or name, and the system runs a broader search. Also check Meta's requirements: the profile must be a professional account (business or creator) linked to a Facebook Page you manage. Personal profiles can't be used for engagement audiences. If you know the profile's numeric ID, you can paste it into the search field. If nothing works, check in Meta Business Manager that your user has access to the profile, and reconnect your Meta account in Ads Editor.