The finger possitions are as follows: 
 
1 = E A D G B e 
    | | | | | | 
    ___________ 
    | 1 | | | | 
    ___________ 
    2 | | | 3 4 
    ___________  
 
2 = E A D G B e 
    | | | | | | 
    ___________  
    | | 1 | | | 
    ___________ 
    | 2 | | 3 4  
 
3 = E A D G B e 
    | | | | | | 
    ___________ 
    | | | 1 | |  
    ___________ 
    | | | | 3 4 
 
A is an upstroke and v is a down stroke. 
 
So strumming is 1. v v vAvA vAvA 
                2. v v vAvA 
                3. vA vAvA   
Enjoy!