First you need to register the extension by adding the following line to your application.
$twig->addExtension(new Twig_Extension_Perch());
Now to use the Perch Extension in your templates you first need to call the runtime using…
{{ perchRuntime() }}
Then add the following code in your template where you would like Perch content to show.
{{ perchContent('Intro') }}
Replace intro with whatever you want your region to be called.