Wipe down the edge of the cutout with acetone. Be sure to wear gloves for protection.
Using a caulk gun, apply a bead of silicone along the edge of the cutout.
Place the sink on the silicone, hold it in place and tighten the wing nuts.
Dry fit the countertops first to make sure the seams align.
Leave the seams slightly apart, and then to ensure a perfect fit before sealing the seams, a tool called a vacuum clamp is used. These are high-powered suction cups that literally pull the countertop seams together.