If it is for an Opel Corsa C 2006, you should either go to an electrician because its circuit is strange, or you should open the screen that has the clock and find which wire has power (using a tester) so you can cut the protective surface and connect the radio's power there. However, be careful not to damage it, otherwise you won't have a clock, etc. Also, if the key doesn't come out, the radio won't turn off! That's it!