Do you have to do it via youtube itself ? If yes, then you will have to enable "Live" streaming feature in your account. Looks like you will have to be eligible to have it enabled.
http://www.youtube.com/live/all
If its enables, you can push your pre-recorded video files to the google's publishing point. For that you can use any supported media encoders. More info can be read here on how to set it up.
https://support.google.com/youtube/answer/2907883?hl=en&ref_topic=2853713
Once thats setup, you can stream events as if its a real live event !