@covershows WP-Piwik is just a plugin to connect your WordPress with the Piwik analytics software. You need WordPress and Piwik, otherwise you are not able to use the plugin.
To get Piwik, you have to install Piwik on your webserver (like you did with WordPress) or to subscribe . You can get all information about Piwik here: https://piwik.org/ – a full documentation is available here: https://piwik.org/docs/, and you can get support here: https://forum.piwik.org/
If you setup Piwik on your own (self-hosted) (as described in the Piwik documentation), it’s absolutely free. After Piwik is installed, you can follow the documentation (https://piwik.org/blog/2015/05/wordpress-integration-wp-piwik-1-0/) to configure WP-Piwik: You need the URL, which you use to access your Piwik (e.g., https://www.example.com/piwik), and the auth token. Afterwards, if you don’t want to change your WordPress theme’s source code, go to the tracking tab and activate the tracking… so WP-Piwik will manage this for you.
Additionally, the Piwik team offers a Pro (cloud-hosted) version, which means they will take care of everything and give extended support. But keep in mind this version is only free for 30 days! If you are using Pro, you just have to enter your auth token and your Piwik Pro user name. (And to activate tracking, of course. ;-))