We have a 14.5 Craftsman lawnmower. When we turn the key on it just clicks and will not start. At first it tried to start but wouldn't, now it just clicks.

Sounds like the battery might be dead. I'd check that first.

If this is the first time you have started it this year, then you may need to hook a charger up to it to get it going.

I agree, battery is very low. Charge it but if it still won't start then replacing the battery may be needed.