Hi ANIL Baral,
You will need to configure the pop-up title of the feature service you want to edit.
You can read more about it here:
From the live example you have provided, if you use dev tools (usually F12) on your web browser, you can add a breakpoint at line 54 and then toggle the popup so that it is visible. After which you can see that the pop-up title for that 'Hazards' layer is using attribute 'Hazard Type' as the title.