open .htaccess and apply this code
this Setting “expires” tells browsers downloading these files that they don’t need to request it again for this specific length of time. In other words, use the cache instead if you have it. This can reduce stress on the server for you, and speed up page load time for visitors.
# BEGIN EXPIRES
<IfModule mod_expires.c>
ExpiresActive On
ExpiresDefault “access plus 10 days”
ExpiresByType text/css “access plus 1 week”
ExpiresByType text/plain “access plus 1 month”
ExpiresByType image/gif “access plus 1 month”
ExpiresByType image/png “access plus 1 month”
ExpiresByType image/jpeg “access plus 1 month”
ExpiresByType application/x-javascript “access plus 1 month”
ExpiresByType application/javascript “access plus 1 week”
ExpiresByType application/x-icon “access plus 1 year”
</IfModule>
# END EXPIRES