The first thing you do if your toilet is leaking at the base is stop using it. The water that’s leaking from the bottom is dirty water, which was in the bowl when it was used. This water may have an odor to it and may be causing damage to the subfloor, so the best course of action is to stop using this toilet, if possible, until you’ve been able to repair a leaking toilet.
First, check the toilet, and make sure that the leak is not coming from somewhere higher on the toilet, causing water to drip down the sides and pool on the floor.
One reason the toilet could be leaking at the base is that the t-bolts, which fasten the toilet to the floor, need to be tightened. Simply remove the plastic covers at the base and tighten the bolts, being careful not to overtighten and crack the porcelain.
In addition to the t-bolts, toilet leaks also indicate that you may need a new wax ring to seal the section the connection between the toilet and the drain pipe. After purchasing a new wax ring, shut the water off to the toilet, disconnect the water supply line, unscrew the t-bolts, remove the toilet and place it on its side. Clean away the remains of the previous wax ring and place the new one on the bottom of the toilet. Then reset the toilet, tighten the t-bolts and replace the caps. Reconnect the water supply line and turn on the valve. Test the toilet for leaks.
If you were unable to repair a leaking toilet, contact a plumber for professional assistance.