Being a DIY person is great and a very noble art but before you read this always know you limits and don’t feel like a failure if you cannot do it yourself. There are sound professionals out there like Archway Plumbers ready to help you. Most of the time a sink will fit perfectly in a pre cut countertop opening, but test fit the sink and check that it sets level. Apply plumber’s putty around the sink’s drain hole and seat the strainer assembly. Flip the sink upside down, tighten the drain nut and “tailpipe” piece. Place the sink upright and install the taps, valves, and handles. Tighten down these items and connect up the water lines to a tee type fitting. You can also connect up the water lines coming into the valves and avoid doing that once the sink is set. Set the sink in the hole and fasten any included mounting clamps underneath it. Run a bead of sealant caulk around the edge. If the sink isn’t self-rimming, run a bead of plumbers putty as carried by an Archway Plumber on the bottom of the lip and caulk the opening to keep water out. Seat the sink and tighten any clamps.Remove any packing that you have used to block the drain whilst carrying out this job. Screw on a trap to the adapter threads and sink drain. Screw on water supply lines (if you haven’t already) and attach them to the shut-offs. Use a “two-headed” shut-off if you’re also going to connect to a dishwasher. Finally it is good practice to run some water down the drain to block sewer gases, and check each line and drain joints for leaks.