Mở Facebook. Đi đến ảnh mà bạn muốn tải xuống. Nhấn vào hình ảnh để mở. Nhấn và giữ lâu trên ảnh. Nhấn vào Save Photo (Lưu ảnh) khi hiện ra.

Given the above summary, write a detailed text in English for it.
Tap the Facebook app icon, which resembles a white "f" on a dark-blue background. This will open your News Feed if you're logged into Facebook. If you aren't logged into Facebook, enter your email address (or phone number) and password when prompted to log in. Scroll through your News Feed until you find the photo that you want to download, or go to the profile of the person who posted the photo to find it.  You cannot save cover photos on Facebook. You can go to a person's profile by tapping the search bar at the top of the Facebook page, typing in the person's name, tapping their name in the drop-down menu, and tapping their profile in the results. Doing so opens it. A pop-up menu will appear after a second or two. It's at the top of the pop-up menu. Doing so will save the photo onto your phone or tablet.