There doesnt seem to be any brackets. We attached the cabinet to the wall and attached the drain and water supply but the sink itself isnt secured to anything and doesnt seem safe.
Most sinks have a backsplash going up the wall a few inches. You can use industrial adhesive to attach it to the wall (like Liquid Nails), then use more of the adhesive to attach the sink to the top of the cabinet.
If the sink is round or oval shaped and sits in a cutout, then you put a bead of caulk all the way around the bottom surface of the sink flange and press down into the hole. You remove the excess caulk with your finger leaving a nice rounded fillet. The caulk will act like a glue to hold the sink firmly to the countertop.
If the sink sits in a cut-out in the top of the cabinet, the plumbing should pull it down tight enough. It should all be adjustable for that purpose. If it sits on top of an open cabinet, the answer above should work. Caulk it to the back wall and to the top edges of the cabinet and then, again, adjust the plumbing to hold it down tight. By adjust I mean, the drain is on a telescopic system where as you loosen the collar, push the sink down tight and then tighten the collar. The water feeds can then be bent to pull them up tight too.
