Search by clicking on the Search (magnifying glass) icon in the title bar. Type any string in the next screen to search through the traffic data. A list of all entities found matching the string appears below it.
Entity found in the search support the following actions:
View Top Conversations -- Displays the top n conversations for the selected entity.
Show Detail View -- Displays a top level detail view of the selected entity.
Add to Current View -- Adds the entity to the current view and drills down to it.
The Settings button (the gear in the upper right corner) lets you confine the search by types (All, Applications, Protocols, and so on).