Now the song is well known but if your'e starting out in guitar 
heres the easy ver. for you! 
 
It consists of the following which can be played on any 
string. The numbers are the frets. 
 
0 - 3 - 5 
 
0 - 3 - 6 - 5 
 
0 - 3 - 5 - 3 - 0 
 
 
When you get the hang of this play it on the middle  
2 strings. 
 
I hope you enjoy!