well, if you got a green bike then the black thingamajig must be your problem....
All joking aside, the poster needs to give better information if he wants someone to help him via the internet.
From the little info that has been posted it seems he has a Grubee kit installed, with the motor chain removed, and the rear wheel wont turn. So he is dealing with a bicycle issue that has nothing to do with his motor assist system....
That said, I would guess the most obvious thing to check would be the brakes! Does it have a coaster brake?
First thing I would do is pull the rear wheel off the bike, at this point it should be pretty simple to see how the wheel should roll on the axle, if it doesn't then you are holding your problem! From there you need to take the wheel to a clean work space and do some investigation, you might need to pull the axle and see what is going on in there...
A year or so of reading posts from newbies has taught me not to overlook the obvious. Is your (motor side) chain tensioner jammed in your spokes? Are your brakes jammed? etc, etc...
