Remove any stagnant water that has been sitting in your bird bath. You don't want to start circulating old water.
Wipe down the inside of your bird bath with a rag. Don't use soap as traces of it may be left behind. Soap is not good for the birds, and water and a rag is really all you need to clean it.
Fill the bird bath back up with fresh water from your garden hose. This is the water you want to circulate to keep the mosquitoes away.
Place 2 D-cell batteries in your Water Wiggler and turn it on. Set the Water Wiggler in the bird bath. The Water Wiggler circulates the water 24 hours each day to keep mosquitoes from breeding in the bird bath.