Spoilers for S08E04 below, obviously. Read at your own risk.
At what part of the episode?
We can't truly know, but we can assume a reasonable amount of time between each event.
Burning of the dead: ~12 hours after Night Kings's Death
Celebration feast: ~24 hours after Night Kings's Death
First War council: ~1-3 days after Night Kings's Death
Army leaving Winterfell: ~2-5 days after Night Kings's Death
Death of Rhaegal: ~1-2 weeks after Night Kings's Death
Death of Missandei: ~2-3 weeks after Night Kings's Death
Each of these events is separated by a hard cut for all POV characters, allowing for arbitrary amounts of time between them. This is the magic that allowed Ned to get all the way down the Kingsroad (a month long journey) in a single episode (S01E02). This differs from reality-bending time-travel/teleportation like Daenerys rescuing Jon and Co from the Lake Battle, because in that instance, we didn't have a hard cut, that whole sequence was implicitly stated to have occurred in however long it takes for a human to die from hypothermia. If, when Tyrion had been talking at Cersei, he had said something like "we killed the Night King three days ago and can melt you at will, please give up", then we would have time problems. But since the show didn't specify a timeline, we can allow that the mundane travel and general boring day to day events happened out of sight whenever the scene cut.
We do know that the events of S08E04 were accelerated because Sansa was complaining about rushing the army and not giving them time to recuperate. We know that the "peace talks" where Missandei died happened in under a month, because Jon (who was traveling the Kingsroad) wasn't there yet. Also, we saw the repairs of Winterfell underway in the episode, so we know they were working on it. No reason from a storytelling point of view to give us a play-by-play on that progress.