It is very simple to use. After installing the add-on, open bookmark. Right click on a bookmark link or folder and then choose ‘Encrypt this link’. It’ll ask you to input password.
Enter a password and click Ok to save the settings. If you want to rename the bookmark, don’t forget to check the box against ‘Rename link’.
Now, whenever a user clicks this encrypted bookmark link, it’ll ask to enter password. Link Password can be downloaded at Mozilla add-on repository.