You can find the Play Store in your list of apps. The icon looks like a shopping bag with the Google Play logo on it. This can be found at the top of the Play Store screen.  There are lots of other scanners available you can try as well. Most work very similarly.   This button appears after the app has downloaded and installed.

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Write a summary of the previous text in Vietnamese:
Mở Cửa hàng Play Store trên thiết bị. Nhấn vào thanh Search (Tìm kiếm). Nhập barcode scanner. Nhấn QR & Barcode Scanner từ Gamma Play. Nhấn Install (Cài đặt). Nhấn Accept (Chấp nhận). Nhấn Open (Mở).