You don't need to do anything. The mushrooms will soon disappear on their own, or you can just sweep them off if you don't like them. Treating with a fungicide will not help as the main body of the fungus is the mycelium, a dense mat of white threads under the ground and the toadstools are just the fruiting body of the main "plant". Its very common at this time of year for these to pop up and they will probably be back next autumn. Most of them are harmless and the poisonous ones are only harmful if you eat them.

Agree with previous answer - don't bother with a fungicide, it won't make any difference, the mushrooms/toadstools will disappear on their own anyway.