Actually there is no such thing at the moment. The program is pretty straight forward, and I don't suspect people not to understand it. If I'm wrong, please leave a message at the "support" page. When the program is started without a file as argument, a dialog will appear asking for a karaoke file to play.
Since this works rather time consuming, I'd suggest setting PTKaraoke as the default for opening *.kar and optionally *.mid files. Now you can use your file browser (e.g. "My Computer") to search for karaoke files and double click one to start playing it with PTKaraoke.
Tip: Enhance the sound of midi
There is one disadvantage to midi files: They sound ugly on a computer. Well, with a bit of luck your soundcard has some options which can enhance the sound. First of all you might be able to use your soundcards hardware equalizer. Second you might try the "virtual environment." Setting this to "parking garage" or "isolated chamber" makes the sound a lot more powerfull.
To access these features you might need to download your soundcard's driver. Changes are you use the soundcard of your motherboard. In this case you can download the driver from the website of your motherboard's manufacturer.
* the pencil...where a lot began