Article in English: If you used the password which came with the router when initially setting it up, you can usually find the password by checking the router or its documentation. If you changed the router password at any point in the time you've owned the router, you'll need to use a different method. Most manufacturers place the router's password on a sticker that's on the back or the bottom of the router unit.  The password is usually near the "SSID" heading. In most cases, the password will be a long string of letters and numbers, both upper-case and lower-case. In the unlikely event that you still have the router's original packaging and manual, you may be able to find a copy of the login sticker inside the packaging, listed in the manual (or on the back of it), or on a separate card which was included with the router. This is only necessary if you can't find the stock password on your router. Unfortunately, you cannot look online for your router's documentation, as your router's password is unique to your model. Most routers allow you to connect by pressing a "WPS" button on the back of the router and then selecting the network on your computer, mobile item, console, or entertainment unit. As long as you select the network within 30 seconds or so, this will allow you to connect your computer (or other item) without need to know the password.  Not all routers have this feature, so check your model's included (or online) documentation for a WPS (or Wi-Fi Protected Setup) feature. This step won't help you figure out the Wi-Fi password, but it will allow you to connect to the Internet on the connected item, which can help you find the password using one of the other methods listed below.

Summary in Vietnamese:
Xác định xem bạn có dùng mật khẩu mặc định của bộ phát Wi-Fi hay không. Kiểm tra bộ phát Wi-Fi để tìm mật khẩu. Tìm mật khẩu trong sách hướng dẫn hoặc hộp đi kèm với bộ phát Wi-Fi. Thử dùng lựa chọn bỏ qua mật khẩu để kết nối.