How to cache a site?

Question

PHP

Google PageSpeed ​​Insights recommends caching to me
but I only have 6 pages on my site and there is no engine.
What and where should be registered as a setting to be caching for a period of a month?
placed in the root of the site .htaccess
with the following content

<IfModule mod_expires.c>
    ExpiresActive On
    ExpiresDefault "access plus 1 month"

    ExpiresByType image/gif "access plus 1 months"
    ExpiresByType image/jpeg "access plus 1 months"
</IfModule>

but nothing has changed in PageSpeed, we still offer caching

Answer 1

To make Google speed happy)

<ifModule mod_headers.c>
    <FilesMatch "\.(js|css|ico|gif|jpg|jpeg|png)$">
        Header set Cache-Control "max-age=604800"
    </FilesMatch>
</IfModule>