Where is the documentation?

It tells me how to install the plugin and get a google API key, but how do I make it execute and get the pageview counts for a post?

The topics here say use

echo gapp_get_post_pageviews();

but does that just get the counts for the page I’m on or what? Are there any arguments for that function?

https://www.ads-software.com/plugins/google-analytics-post-pageviews/