Just import in your component
import "package:polymer_datepicker/polymer_datepicker.dart"
and use in your html :
<date-picker selected-date="{{myDate}}" onlydate="true" label="Choose a date" on-selectdate="{{dateSelected}}"></date-picker>myDate should be an observable DateTime property. Observable feature is supported using polymer_autonotify.
This component uses intl package for week days and month names therefore locale should be properly initialized before using it (see intl library for more info).