Add a language selection

Hi there,
We are working on the theme Sailing, and we cannot find how to add the possibiliy to switch languages on the main menu.
We actually work on the demo 8, and we would like to add this option like in the demo 5 (Sailing | Powerful Management Hotel Booking WordPress Theme | Demo 5)
Please let us know how to activate this option, thank you


From what I understand you need this: