This is a PHP class, so obviously all code that uses it is in PHP, so you just need to look at the example scripts for instance starting with the Example tab. It contains an example script with comments that should get you started quickly.
phpclasses.org/package/1-PHP-HTML-f
...
If you prefer a tutorial, there is this old but still current video tutorial. It is long but it has links for you to jump to different sections. I apologise for the sound volume that is a bit low, so you need to amplify your audio enough to listen clearly.
phpclasses.org/package/1-PHP-HTML-f
...