Go to https://www.google.com/preferences in any web browser. Your browser must have cookies enabled in order for it to save your preferences when you exit. You'll find it near the top of the page.  If SafeSearch is locked in your browser, you will need to enter the password when prompted. If this box is already unchecked, SafeSearch is disabled on your computer. It's in the middle of the page. This setting isn't directly related to SafeSearch, but it will ensure that you see a larger variety of relevant images. Again, if this box is checked, it's already active. This blue button is at the bottom of the page. Doing so will save your settings and return you to Google. Search for your preferred term or phrase to determine whether or not SafeSearch has been disabled. If you see explicit (or even different) results than before, you've successfully disabled SafeSearch for Google. If you still aren't seeing explicit content, your ISP or region may be blocking explicit results. You can contact your ISP to inquire, or you can use a VPN or proxy to view blocked content.

TL;DR in Vietnamese:
Mở trang Cài đặt tìm kiếm của Google bằng cách truy cập https://www.google.com/preferences từ trình duyệt bất kỳ. Bỏ chọn ô "Turn on SafeSearch" (Bật SafeSearch) ở gần đầu trang. Đánh dấu vào ô "Use private results" (Sử dụng kết quả cá nhân) ở giữa trang. Kéo thanh cuộn xuống và nhấp vào nút Save (Lưu) màu xanh dương ở cuối trang. Thực hiện thao tác tìm kiếm.