Recently my friend check his website in Google page speed test tool. It show advice to make Leverage browser caching. I new to web optimization. So what is Leverage browser caching and How to use them.
Need Advice..

Leverage browser caching increase your website page loading speed. Every browser need to load and render several thing such as logo, images, CSS files and JS files. Each page visit need this same thing. But if you make Leverage browser caching, your browser remember your webpage resource which is already loaded.
This mean if you are your visitor goes to any another page in your website, browser doesn’t not need to get your website resources (CSS, JavaScript files, image etc) again. So your website page load speed increased.

Login in your website C panel. Find you website directory and Add this code in your website .htaccess file. if you not see any .htaccess file check your web hosting file manager settings. Some times it hidden.

<IfModule mod_expires.c>
ExpiresActive On
ExpiresByType image/jpg "access 1 year"
ExpiresByType image/jpeg "access 1 year"
ExpiresByType image/gif "access 1 year"
ExpiresByType image/png "access 1 year"
ExpiresByType text/css "access 1 month"
ExpiresByType text/html "access 1 month"
ExpiresByType application/pdf "access 1 month"
ExpiresByType text/x-javascript "access 1 month"
ExpiresByType application/x-shockwave-flash "access 1 month"
ExpiresByType image/x-icon "access 1 year"
ExpiresDefault "access 1 month"

If your friend already using any WordPress CMS, don’t need to go website C panel to edit .htaccess file.
There are many plugins available to edit WordPress .htaccess file. One of the WordPress plugin is
WP htaccess Control. You can easily edit .htaccess file in your WordPress Admin dashboard.

Use this links to get get some detailed information about Leverage browser caching from Google.