Once you have added your user stories, the next step is to prioritise them, taking into account which user stories are required by other user stories. Drag user stories on the story map to the desired position on the map.
You can place items on either side of existing items, as well as above or below them. A red bar is displayed to indicate where the item will be positioned:
In this case, the “Search for books” item will be placed to the right of the “Find recommendations” item (the red indicator is to the right of the existing item):
You can now prioritise your work items visually, and assign different items to different iterations/sprints based on their priority: