As a reminder, it is the Product Owner who is responsible for translating a user request or need into a user story, in as detailed and clear a manner as possible.
They will therefore present to the rest of the team the US that they have completed, or at least those that are already well advanced.
The aim is to ensure that the members of the development team have a perfect understanding of the requirements and that they have the opportunity to ask questions and discuss these US.
The Product Owner can then modify or enrich them following the questions and discussions that have taken place.
The team can then validate the user story and move on to its estimation.
👉 If it turns out that the development team does not understand the request, the Product Owner will have to take time to rework and clarify their US to present them again during the next session.