Flexbox is a CSS3 module, standardized by the World Wide Web Consortium. It is a layout mode for element arrangement such that the elements behave predictably when the page layout must accommodate different display sizes.
Because it is a part of CSS3, you don't need to install anything. It can be used as long as the browser supports it, and most modern browsers do. To check if your browser supports it or not, here is the compatibility chart.
To set up and use
flexbox in your CSS, simply add
display: flex to a selector.