Hi @rituk49412512,
As per my understanding either you want to track when the users click on a dropdown or just the values present in the dropdown.
In case you want to track click on dropdown you can create an Event Based rule which will trigger on click event for the dropdown.
In case you want to track items in the dropdown you need to populate a ListVar by populating the values in dropdown to a Data Element and then using that Data Element to populate the list var with a statement as follows:
s.listVar1 = _satellite.getVar("Name of Data Element");