It's a gray app containing gears (⚙️) on your home screen. It's near the top, next to a red icon with a white square inside it. The apps are listed in alphabetical order. It's in the second section on the screen and will turn green. Make sure Allow Notifications and Show in Notification Center are also turned on. It's the round button below the screen. Doing so from the home screen opens the "Today" section of the Notification Center. It's a round button below all the selections. The apps in the second section are listed alphabetically. This adds the Weather widget to the Notification Center.  A red circle means the selection is already included in your Notification Center. Scroll up to the top of the screen, and hold the "≡" next to Weather to slide it up or down, changing its position in the Notification Center.

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Write a summary of the previous text in Vietnamese:
Mở mục Settings (Cài đặt) trên iPhone. Nhấn Notifications (Thông báo). Cuộn xuống và nhấn News (Tin tức). Trượt nút bên cạnh "Show on Lock Screen" (Hiển thị trên màn hình khóa) sang vị trí "On" (Bật). Nhấn nút "Home" (Trang chủ). Vuốt sang phải. Cuộn xuống và nhấn Edit (Sửa). Cuộn xuống. Nhấn nút màu xanh lá ⊕ bên cạnh mục Weather (Thời tiết).