Basically this is just a tutorial on how to play that riff that everybody knows.
Step 1: The First Note
The first note you play is C. Look at the picture below to see where that is if you don't play piano.
Step 2: The Second Note
The second note you play is D#. Again, look at the picture below to help if you don't play piano.
Step 3: The Third Note
The third note of the song is F. Check out the picture for help.
Step 4: The Fourth Note
This is the fourth and final note in the riff. The note is F#. Check the picture for help, as always.
Step 5: String It All Together
Now to play the song is simple. All you have to do is correspond each note to the number in the order I gave them to you. So the first note in the instructions would be 1, the second would be 2, and so on. The song goes like this (you probably want to know the rhythm of the song to make it sound better, though): 1 2 3 1 2 4 3 1 2 3 2 1. It's as simple as that! Good luck!