Once you have the proper hole cut in the countertop, it's time to install the sink. You could put in the sink and then attach the faucet, garbage disposer, and drain from below. But it's much easier to attach those elements to the sink first, then put the whole assembly in place.
Spread a drop cloth on the countertop and set the sink upside down, with the faucet holes overhanging the edge. Or set the sink on two sawhorses, padded with rags or towels.
Enameled-steel and stainless-steel sinks clamp to the countertop with special clips that are usually included with the sink. Test to make sure that the clips will work on your countertop before you install the plumbing. A cast-iron sink is heavy enough to stay in place without clips.
About half a day to install a sink with disposer and dishwasher connections
Drill, screwdriver, groove-joint pliers, adjustable wrench, strainer wrench or spud wrench
Connecting a trap, installing a faucet and garbage disposer
Install the rough plumbing, a switched receptacle, and the cabinets
Sink, faucet, garbage disposer, appliance extension cord, wire nuts, trap assembly, supply tubes, flexible copper line for dishwasher and icemaker supplies, drain hose (usually included with the dishwasher), air gap, plumber's putty, drop cloth
Install a standard basket strainer in one sink hole and the garbage disposer strainer in the other hole. Make sure you know which strainer goes to which hole. Place a rope of putty under the lip of the strainer body and hold it in place as you slip on the washers and tighten the nut.
Assemble the drain pipe. Begin by installing the tailpiece and the arm that attaches to the disposer. Cut pieces to size as needed, then install the trap. Set the sink in the hole to see whether the trap lines up with the trap adapter in the wall; you may need to trim a piece or add an extension.
Screw flexible supply tubes onto the faucet inlets. Make sure that the tubes are long enough to reach the stop valves, and that their ends are the right size to screw onto the valves. If the faucet has flexible copper inlets, use two adjustable wrenches to avoid kinking the inlets.