It is a clicking sound
By turning the ignition key...
So it would seem. If the ignition is in the column it may also be jammed by the steering wheel lock. Try turning the steering wheel and holding it while turning the ignition key.
With a key, by turning on ignition
You have a flat battery.
try turning the steering wheel to the left or right and holding it there while turning the key
The key and the ignition lock are badly worn. Try a different key if it doesn't fix it you need to replace the ignition lock.
Unlock the ignition? Is the key not turning? This car has a steering lock, but if the key is not turning you probably have either a bad key or a bad EIS (electronic ignition switch) make sure you check it with BOTH keys first, if you have another one.
Physically has a turning problem ? Try your spare key and still has the problem? Replace the ignition switch.
Try spraying a lubricant of some sort into the key hole and turning the key back and forth. Otherwise you'll need to take the ignition out and take the whole thing to a locksmith.
I would have the ignition itself replaced. These go out all the time and will leave you stranded. Get a new ignition keyed to your current key and you won't have to do programming. A locksmith can do this for you. Do it soon though before it stops turning.
TRY TURNING THE KEY OVER.
It is likely broken.