Normally, tourist standing in the square to watch the ceremony, they are also facing to the HKCEC, so you can see a crowd in the left side of the video. The flag rising ceremony is normally organized by the Hong Kong Police, the nation anthem is playing while the regional flag of HKSAR and the national flag of The People's Republic of China.
The tourist association promotes this event very much. If you are living in Kowloon side, simply go to Tsim Sha Tsui and take Star Ferry to Wan Chai. The "Golden Bauhinia Square" and HKCEC is besides the ferry pier.