Do you mean that when you turn the key all that happens is a click?
Do the dash lights dim or go out when you turn the key?
If they do - it sounds like a flat battery.
Put a trickle charger on it overnight.
Have you got a digital volt meter - if not get one at Halfords - a cheapy one will do.
You need to find out if it is perhaps a new battery that is needed or if some other problem exists, but until you have tried charging the battery - we can't move on.
if the lights dim when you turn the key, if the clock goes to 0:00 it's probably the batery;
if it hapens after a 30 minute drive and a 5 minute stop and at 3rd or 4th key turn it starts normally it's probably the solenoid in the starter.