The critical elements of the original Forster & Davis (1984) display are:
In the first demonstration, the prime is displayed for 40 ms (the precise duration will depend on the properties of your computer). Sometimes, the prime will be the same word as the target (a case of repetition priming), sometimes it will be different.
Can you tell which is which?
In the second display, the prime is on for longer (approximately 100 ms), and you will probably be able to tell whether the prime is the same as the target.