At this time, there's no option to automatically publish livestream replays.
To publish a past livestream, you'll return to the Publish screen under the Go Live tab.
From here, you'll select Choose Replay. If no replays appear, you can refresh by selecting Check for Replays.
From the menu, you'll select the livestream replay you want to publish, enter in the requested information, and select Create at the bottom of the page.