After installation, You will be able to see the two date fields, wherever there will be a date field in any module that would be installed at that particular instance.

The first date field is the base date field for English date picker and the below one is for the Hijri date picker field.

As you can see in the above screenshot, there will be two date fields, from which if you select the first date field it will open up the English calendar date picker.

After that, when you select a particular date then that date will be set to its respective field as well as in the below field that date will be stored according to the Hijri(Islamic) calendar.

As you can see in the above screenshot, there will be two date fields from which if you select the second date field it will open up the Hijri (Islamic) calendar date picker.

After that, when you select a particular date then that date will be set to its respective field according to Hijri date picker as well as in the above field that date will be stored according to the English calendar.