Where do I start to find out why I cant get car started after flooded in water ? on 2000 Cadillac Seville STS

I went through a bridge with water & it got washed into the stream & now car wont start & I have replaced the battery just makes a clicking sounds . what do I do next to find the solution ?

Asked by for the 2000 Cadillac Seville STS
How deep was it submerged? If water was over the hood and inside of the car, most likely a total loss! Contact insurance co.