The Detail view displays one item at a time. It can only be reached through one of the following views: Gallery, Grouped Gallery, Point Map, or Scatterplot.
In the "Views" tab of your visualization, click the "Detail View" thumbnail to configure a Detail view for your visualization.
The configuration window will appear with the settings for the Detail view. Here you can toggle the fields that you want to display in the Detail view on or off.
The fields you have selected will appear in the Detail view when you access it via one of the other views listed above.
Any fields that you have setup as filters will appear as links, and clicking them will take the user back to the default view of your visualization with the selected filter applied.