The webpage says

Loads a text file that contains two numbers separated by a tab ('\t'). A new pair of numbers is loaded each frame and used to draw a point on the screen.

so why not create your own textfile using a simple text editor e.g. NotePad. The example code expects the file to be called positions.txt but you could change it to anything you like. Make sure you save the file inside the folder for the sketch.

You need to provide more information if we are to help you.

Describe what went wrong?
Did a second window open when you ran the sketch?
Did you get an error message (these appear in the bottom panel of Processing)?

Try

Glad to hear that!