It is easier to put the faucets in before you install the sinks. For a typical three-piece faucet, run a flexible water supply line (Image 1) from the house to the base of each faucet.
Next, connect another flexible line from each valve to the mixer. As the cold water comes from the house, it goes into the cold valve. When the cold valve is opened, the water flows into the mixer (Image 2).
The water mixes with any water from the hot side and then comes out the spigot.
To attach the faucets to the sink, we remove the handles from the valves. Remove the top bezel and install the valve from the underside of the sink. Screw the bezel back onto the valve. A rubber O-ring on the bezel (Image 3) eliminates the need for plumber's putty or silicone.
Put the handle back on and repeat for the other side. If the handles don't line up properly, put them both in the off position. Then, take off the crooked handle and line it up and put it back on.
To install the central spout, start by removing the mixer, the attaching nut and rubber washer. There is no O-ring here, so you need to use plumber's putty to create a good seal. Plumber's putty never hardens. Roll the putty into a snake and wrap it around the base of the spout. If there is excess putty, it will squeeze out when the fitting is compressed.
Put the spout through the sink. Attach the washer and nut and reconnect the rest of the fittings and you are ready to go.
Line up the front lip of the sink and drop it into the countertop nice and easy.
Take a putty knife and scrape off any excess plumber's putty that you applied.
After you attach the water line, take some beaded silicone and make a good seal.