add tracking url with event type inside <TrackingEvents> of VAST xml file to collect data. 

<TrackingEvents>

    <Tracking event=”start”>https://example.com/tracking/start</Tracking>

     <Tracking event=”firstQuartile”>https://example.com/tracking/firstQuartile</Tracking>

     <Tracking event=”midpoint”>https://example.com/tracking/midpoint</Tracking>

     <Tracking event=”thirdQuartile”>https://example.com/tracking/thirdQuartile</Tracking>

     <Tracking event=”complete”>https://example.com/tracking/complete</Tracking>

     <Tracking event=”pause”>https://example.com/tracking/pause</Tracking>

     <Tracking event=”resume”>https://example.com/tracking/resume</Tracking>

     <Tracking event=”skip”>https://example.com/tracking/skip</Tracking>

     <Tracking event=”clickthrough”>https://example.com/tracking/clickthrough</Tracking>

</TrackingEvents>