First welcome to Sailnet and sailing. I'm not familiar with the boat that you bought but if like a Sunfish the cockpit drain is of the self bailing type. You would open it when you are moving and the water drains out. If you are getting water into the hull then it sounds as thou you might have a problem, maybe taken apart and re-bedded. You might want to make sure the hull is dry before reinstalling.
Have fun sailing