how 2 make the rear cog move the wheel?

Hi Emma.
Can you turn the pedals, the chain and back sprocket turn, but the wheel doesnt ? If so, the freewheel (back sprocket) is not working inside. Did this happen during the icy weather. They can freeze, then be ok when its warmer.. If it is as above, a bike shop can fit a new freewheel.
If it did happen in the cold, it may never happen again, it may come back in the cold. It'd probably be ok though

Any more information may help us to assist you

Colin
January 2011

We're assuming the chain is attached. The cog is attached to the wheel, so if everything else is working, then it should turn when the chain turns. If the back wheel won't turn, check to make sure there is clearance between the cog and the frame. There needs to be a nut that protrudes beyond the cog to create the space.

Papa Wheelie
January 2011