Before implementing application, refer to https://pub.dev/packages/image_picker.

1.Add package using flutter pub add image_picker
2.Create varialble imagePicker using ImagePicker()
3.Use pickImage method in imagePicker class that you can use camera on your device
4.Don't forget this is a asynchronous function
5.Update state using setState and set File variable
6.To show picture, use FileImage

That's all you need to follow. Please revise here if you forget.