Fixing A Leaky Tank
1. Shut off the water supply to your toilet by turning off the local shut-off valve. If you can't find this, you will have to turn off the main water supply to your house. Drain all the water from the toilet tank by flushing. Any remaining water can be soaked up with towels.
2. Check to see if your toilet tank is attached to your wall. If it is, get some pliers and tighten those couplings that you see on the pipe that leads from the toilet to the tank. If these couplings already seem pretty tight, loosen them a bit and remove the pipe. Put new washers on and reinstall the pipe, tightening the couplings securely.
3. If your toilet tank isn't attached to the wall, than in should be attached to the toilet. Look on the ground. Your toilet is attached to the floor with bolts. Get a screwdriver and tighten them. If the leak continues, remove the bolts and get some new gaskets. The gaskets are those little rubber pieces that each bolt keeps in place.
4. If your bowl is leaking at the connection point with the floor, you must remove the bowl and re-seal it where it attaches to the waste pipe. You may want to call in a professional for this job.