To enter a location with a hidden object scene, tap/click on its building on the map.
In the scene, you need to find the items from the search list before the time runs out.
When you enter the location again, the search items may look different and may be found in different places.
Tapping/clicking on objects that are not on the search list two to three times within a second will reduce the time limit for 5 seconds. The time penalty increases with each subsequent mistake.