To use the password lock in the Douyin live broadcast room, you need to follow the steps below:

1. Enter the live broadcast room and click the "More" option at the bottom of the interface to enter the live broadcast settings page.

2. In the settings page, find the "Turn on password lock" option and click to turn it on.

3. Enter the password and confirm it.

4. After confirming the password, the password lock will be turned on, and others will need to enter the correct password to enter the live broadcast room.

Please note that after turning on the password lock, the number of participants in the live broadcast room may be reduced. Therefore, if you need to turn on the password lock, it is recommended to inform the audience in advance and provide the password.