Back light for 2011 250cc

[dublin]

I just bought a back light unit and mudguard of 2011 ec 250 to convert my 2011 250cc i just tried conecting the light all the wires seem the same and conecter fits light comes on fine but the brake light is not working i can see the front brake light is not conected to anything but back light switch seems to be conected i know the light switch on mine is not the same as the ec 250 just want to know is there an easy way to get one of the brake lights to work be gratefull for any help i am not great at wiring