In Agile methodology, user stories refers to a specific feature or function, usually framed from the perspective of an intended user. In P4 Plan, you can implement this into your Agile planning by flagging existing backlog items as user stories.
To flag a user story, right-click an item in a sprint or in the backlog and select Flag as user story. This adds a User story area to the Item details.
It is possible to automatically flag all new backlog items as user stories by default. For more information, see Configuring default sprint settings.