The developers will estimate how many story points it will take to complete a story.
Stories are usually estimated in the Icebox.
If there are more than 5 unestimated stories in the Icebox, you should label the ones that you wish to have estimated with "estimate" before your weekly project meetings.
Once the story has been estimated, the number of story points will show up on the left side of that story.
Please see the FAQ: What is a Story Point? for more information about how points work.