This is the recommended way as you will have a completely separated server where you can track the all your sites. userTrack provides a cloud-init configuration script, which allows for one-click installs or you can follow the shell commands mentioned in it to download and install userTrack.
userTrack was designed to run on any server and even on cheap shared hosting, as long as it meets the requirements. Install userTrack in 4 simple steps:
You can find a more detailed WordPress installation guide here.
Install wp-usertrack.zip as a WordPress plugin and activate it.
Access the userTrack plugin from the wp-admin sidebar.
Choose a password.
Login: user: admin pass: Your chosen password
Add the current domain name to be tracked (eg. yoursite.com).
If your WordPress site is in a sub-folder: go to Settings -> Tracking and click "RESET" next to the Server path setting so that the server API path is automatically detected.
Make sure to check the Pages to track menu to set on which pages to automatically insert the ust.min.js file. It's recommended that you track all non-sensitve pages for more accurate data.
You can also include the ust.min.js script manually and even on different domains (tracking snippet is shown after adding a new domain name, or from the tracker info of existing domains).