How can I avctivate the code number after canging the battery?

My battery went flat. I have changed the battery, but I lost my radio unit.Itried to enter the code without refering to the instructions,but failed and I beleive the processor closed . Iam driving a Polo car model 2001.The agent in Khartoum failed to rpair it.Can you help me? My unit model is Boston C30. When I open the unit the display show " wait one hour . I have waited for hours but still the display shows the same.The unit Model is Boston C30.