This host exists so Zapier can connect to your EasySignage account. There is nothing to use here directly.
Start from Zapier: add the EasySignage app to a Zap and choose Connect a new account. You will be asked to sign in to EasySignage and approve the connection.
Connections appear under Settings → API Keys in your EasySignage account, where you can revoke one at any time. Revoking it disconnects Zapier.
zapier-auth-stage.easysignage.com