Now that the plumbing is in, neither sink will drain. We installed a vent pipe and still won't drain and we don't know what is wrong.

how to install a second kitchen sinkI don't understand. Your presence. Sink won't drain and you think that replacing it with another sink will solve the problem? Sounds like you have a blockage in the horizontal line in the wall. The solution would be to remove the "J" bend from the trap and send the snake up into the wall. You only have to put out about 6 feet of snake. Good luck, Tom