Password pages / posts in WordPress can be done with a text editor, without any additional plugins.
Yes, I also just found out when menontn tutorial on Youtube, and apparently it is a built-in feature of wordpress.

Check the following steps,

• Open your page/post with the editor
• On the top right, select the Publish tab
• Go to Visibility and click edit
• Then select Password protected
• Fill in the password
• Then Publish

Check your page/post in a new window.
You will find a page with a password that needs to be entered to view the content.

Comment below if you made it, guys!