Optimizing your images’ “title” and “alt” will not only give your website better ranking in the search engines, but it is very important for text based browsers, accessibility, etc. to be able to read your images.
To optimize your images, you can use the specialized Joomla extension SEO Friendly Links and Images. This plugin automatically optimizes all of your images, including existing ones, taking the title and description from the post.
For more details on how to install extensions onto your Joomla, please check this article HERE.