if you want to ride freewheel, you need to buy a freewheel.
The only difference between the fixed and free side of the hub is that there's no threading for the lockring on the freewheel side. The ability to freewheel is inherent to the cog itself.
Go to a bike shop, and ask for a shimano freewheel, they're probably no more than £20. Then, take the back wheel off, grease up the threads of the free side of the hub, put a little grease onto the threads of the freehub (not too much mind), and screw it on!
if you want to ride freewheel, you need to buy a freewheel.
The only difference between the fixed and free side of the hub is that there's no threading for the lockring on the freewheel side. The ability to freewheel is inherent to the cog itself.
Go to a bike shop, and ask for a shimano freewheel, they're probably no more than £20. Then, take the back wheel off, grease up the threads of the free side of the hub, put a little grease onto the threads of the freehub (not too much mind), and screw it on!