Answer:

Removing the large debris (leaves and tadpoles, etc.) manually would be the first step. You probably do not want to vac and filter this out unless you can bypass the filter with the waste. Unfortunately, clean up of this extent is not typically quick and is labor intensive. Once the large debris is gone, top up the water and get it balanced and start adding algaecide for green or all algae as well as chlorine (follow instructions carefully for algaecide may go in particular order with your chlorine). The water balance and filtering should clear it up, but again it is not a particularly quick process. It may take a few days to clear up from this point.