Hi,
When you Analyzing your store URL with gtmetrix, it will help to get information about Expires headers in YSlow section.
Below is the link with changes need in .htaccess file.
https://gtmetrix.com/add-expires-headers.html
PrestaShop Tutorials Videos [How to do Tasks]
https://www.prestashop.com/forums/topic/907438-prestashop-tutorials-videos-how-to-do-tasks/