Installing a fiberglass kitchen sink is much easier than installing a porcelain or stainless steel sink because it is much lighter and easier to handle. If you're installing a new sink into an existing sink hole, skip Steps 1 through 4 and begin with Step 5.
Lay the fiberglass kitchen sink upside down on the countertop and place it in the exact position it is to be installed. Center it, but position the front edge of the sink so it is at least 1½ inches from the edge of the counter but not more than 3 inches.
Trace around the outside edge of the fiberglass kitchen sink.
Remove the sink and draw another line 1½ inches inside the outline that you drew in Step 2.
Drill starter holes in each corner of the sink outline with a drill bit large enough to accommodate the blade of a reciprocal saw. Cut out the hole for the sink along the inside line. Have a helper hold the cut-out piece from below so the weight of it doesn't break or crack the countertop material before the cut is completely finished.
Set the fiberglass kitchen sink upside down on the floor or another area of the countertop. Place a bead of silicone plumber's caulk all around the bottom edge of the sink rim (now facing up because the sink is upside down). Place the sink into the cutout made in Step 4. Press it down firmly and securely until the caulk seeps out of the edges of the sink. Wipe off excess caulk.
Install the faucets. Apply plumber's putty around the base of the faucet plate and set it into its hole. Press down firmly until the putty seeps out. Wipe off excess caulk. Place plumber's tape around the connecting threads at the bottom of the faucet and bolt it into place.
Connect the water supply lines. Use plumber's tape on the threads of the connectors. Attach the cold supply line to the cold side of the faucet and the hot to the hot side. Tighten well with a wrench.
Put plumber's putty around the top edge of the basket strainer. Insert into the drain hole at the bottom of the fiberglass kitchen sink and push firmly into place. Wipe off excess caulk. Underneath, attach a washer and locking nut to the threads of the basket strainer. Tighten until the plumber's putty seeps out of the top of the basket strainer.
Attach the "S" drain pipe to the bottom of the basket strainer using plumber's tape and the other end of the drain pipe to the existing drain pipe rough-in.