1) In the creative manager, select "video."
2) You can upload either a VAST tag or video file.
You can paste the VAST tag info here:
Or to upload a video file:
3) You will be shown a preview of the unit:
4) AppNexus automatically adds click tracking to the VAST wrapper. Be sure that the clickthrough destination is specified, per the VAST spec, by your third-party ad server.
5) Add the name of the creative.
6) Add tracking, which is optional.
7) Submit to audit on the platform.
If you have additional questions, the AppNexus wiki has additional information.