Select the event you created. Open the Event Actions drop-down. Choose Event Settings.
Under Event Partner, select WebEx.
Under Login, choose your WebEx login.
Under Event, choose your freshly created WebEx event. Then, select an optional Back-up Page and click Save.
Select an optional Back-up Page for your WebEx event. Choose from the drop-down of approved Marketo landing pages or enter the URL of a non-Marketo landing page.