Nhấp vào ứng dụng nằm ở góc trên, bên phải màn hình. Nhìn vào tên mạng. Xem qua các SSID có sẵn khác.

I'm interested in that, but I only have a few mins. Can you give me at most the first 500 characters of a detailed explanation in English about that?
It's in the upper-right corner of the Mac's screen. If you see here, click it, then click Turn Wi-Fi On. It's the name with a ✓ to the left of it. The name you see here is your network's current SSID. Any network names you see here are the SSIDs of other networks near you.