Doing so will prompt a drop-down menu. This option is at the bottom of the drop-down menu. It's the second link from the top of this window. Doing so will select it as your desktop background.  You can also click the Windows Wallpapers box near the top of the window to pick a different pictures folder (e.g., "Pictures"). If you want to look for a specific picture, click Browse. This section is beneath the "How should the picture be positioned?" heading. Your options (from left to right) include a full-screen version of the picture, a grid comprised of your photo, and a centered version of the picture. It's at the bottom of the window. Doing so will apply your selected picture to the desktop background.

TL;DR in Vietnamese:
Nhấp chuột phải vào hình nền. Chọn Personalize. Chọn Desktop Background (Hình nền Máy tính). Nhấp chuột vào hình ảnh. Nhấp chuột vào tùy chọn vị trí ảnh. Nhấp chuột vào nút OK.