Is it active?

I installed it a few days ago & edit those options as I want to. But can’t understand is it active or not. Checked Google Page Speed Score. The score is same.
Is there any way to find out that it is running or not.
Found this in FAQ “How do I know my blog is being cached?
You need to refresh a page twice. If a page is cached, at the bottom of the page there is a text like “<!– WP Fastest Cache file was created in 0.330816984177 seconds, on 08-01-14 9:01:35 –>”.”
But at the bottom of my page I found nothing.