Change time & date

Hey,

I’ve recently bought a 2011 Citroen c4 VTR plus 1.6 diesel 5 door car. The date & time currently displayed on the radio screen are a series of hyphens (—/—/——) and (—:—). I’ve done the obvious thing & checked the manual & can get as far as the option to “adjust date & time” within the configuration settings, but this option isn’t available to select. When I move through the options this one is half highlighted & im unable to select it. I’ve tried pushing different combinations of buttons but no joy. Can someone please advise how I can get around this?

Thanks,

Henry