Welcome from Highland Park, IL (north of Chicago)!
With a 22" kettle, a 4lb pork shoulder should take about 9-10 hours to reach internal temperature of 200F using a steady cook temperature of 250F. As noted above, use the snake method of arranging unlit charcoal briquettes around the bottom of your grill using a circular pattern around a aluminum pan filled halfway with water. Check out YouTube for step by steps on the specifics - it's virtually foolproof (hell if I can do it, anyone can). If you don't have probe thermometers for the grill temp and the pork shoulder internal temp, you'll want to invest in that as I've found them to be critical to managing a low-n-slow cook. Light one end of the snake using 12 hot pieces of charcoal, dial your vents back (bottom to 1/2 open and top at wide open to start), then wait for the temp to reach 250F then adjust the top vent as needed from there. Wrap the shoulder in foil when it reaches an internal temp of 160F and let it cook in the foil for the rest of the cook. There are TONS of recipes for pork shoulder - find one that sounds tasty for the rub, seasonings, etc. and just go for it! Definitely let it rest before eating - 30-45 minutes wrapped in the foil is totally fine. Good luck and welcome aboard!