Before reading this help file you may want to check this video. It explains theme functionality and may be easier to understand. Watch Video on Youtube
To enable this option you must navigate to Theme Options > Design > Property, Agent, Blog Lists Design and setup yes to Click and open Property Modal Window – Zillow style option.
The option will apply in lists (Properties List, Search Results)
Tip: If you have theme cache enabled, make sure you clear cache to see instant results.