Xamarin.Forms - Can't get geolocation

Hi,
I am trying to use the code from this article:
https://docs.microsoft.com/en-us/xamarin/essentials/geolocation?tabs=android

but "using Xamarin.Essentials" leads to compile-time error:

Error CS0234 The type or namespace name 'Essentials' does not exist in the namespace 'Xamarin' (are you missing an assembly reference?) AndroidXamarinWIFIApp1 C:\prj\Demo\AndroidXamarinWIFIApp1\AndroidXamarinWIFIApp1\MainPage.xaml.cs

What assembly should I add to get rid of this error?