To enable Autoplay on your videos please go to Players page
On the Player page, you will have a list of players in your account.
To enable or disable autoplay click the Edit icon on the right of the player.
In the Autoplay, section selects On or Off.
In the Muted, section selects Off.
Videos that have Autoplay On must be muted in order to play them on all modern browsers
After you finished editing it make sure to Preview player behavior to make sure you got the desired outcome.