Once installed and properly configured, the Protected node module adds a field set in the node edit form (assuming the user has the corresponding permission: "edit any password" or "edit password <node type>".)
This field set includes two flags, a password, and emails (optional.)
By default, the field set is closed unless you selected protected by default. Whether the field set should be opened or closed can selected in the node type settings.
The <node type> is protected
The first check box is used to password