how can i fix this?

If there are no wires already connected to the back of the cooker, it generally means that it needs to be 'hard wired' - that is, directly connected into its own fused supply with 6mm cable. Somewhere on your wall should be the cooker master switch and hopefully below that somewhere there will be a terminal outlet. The 6mm cable needs to be joined at the terminal outlet, but if there isn't one the cable needs to go directly from the cooker master switch to the new cooker.

John
March 2008