Ui Element Variable Pass

Continuing the discussion from How to select a value from dropdown (combobox) of web page:

@Rammohan91 @polina.cherepanova

Where should I pass the variable in Selector Field or Element field?
If I pass it to Element area in the Property its throwing an error "Sting can not be converted to uipath.core.uiElement "

Any Suggestions ?

it should be in the selector.