Download your works catalog from your own PRO account, upload it here, and WritingRoom fills in your credits and marks each one “Corroborated — PRO statement on file”.
One honest note about this badge: the statement comes from you, so it backs up your credits — it isn’t the same as someone else confirming them. Stronger checks are coming and will upgrade these badges on their own. Your uploaded file stays private to you (and WritingRoom support) — only the badge is public.