Well first off.. what is the problem with your phone? The best thing you can do right now to prevent further damage is shove it in a bag of rice to let it soak up the water to prevent as much corrosion as possible.
After 6 hours of hanging out in rice, see whats wrong with the phone.
Is it turning on?
Is the back light dim?
Saira Hafeez, the first thing you want to is to clean your phone. It sounds from your question like the damage is already a bit older. Rice, or any other remedy, will only help in an acute phase. It will only displace some of the water, and will not prevent corrosion. You never want to turn on any device that has had water damage until it is properly cleaned, turning it on may cause short circuits due to corrosion. Follow this guideto clean your phone. It was written for a 3G but all the points still apply to your phone as well. Once you cleaned is properly,'replace the battery and reevaluate for any damage.