If you look for solution that will allow to create password protection for your PrestaShop CMS pages - take a look on this guide. It is based on module to protect CMS pages with password. Addon adds feature to shop that allows to define for which CMS pages you want to create such restriction. Each CMS page can have own unique password (you can manage passwords from module configuration page).
How to create password for CMS page
after that, selected CMS pages will have password feature. If customer will try to view such page - it will be necessary to enter password, otherwise module will spawn information, that page is protected (like on video below).