It's time to connect the new faucet's fittings with the water-supply lines. The manufacturer's instructions may direct you to set the new faucet assembly in place, then crawl back under the sink to make the new connections. Save yourself from struggling in cramped quarters by making all the connections you can before setting the new assembly in place. Then feed the connected lines down through the hole in the sink. With the attachments at the base of the faucet assembly already in place, the only work you'll need to do under the sink is to connect the supply lines to the shutoff valves.