Paintdrying has it right, but use Jam nuts, the low profile ones. Also use all Brass 5/16 Bolts Locate with a straightedge parallel to the wall, bisecting the pipe. Take the tank off and locate the bowl first, Much easier, and you should be replacing the tank bolts anyhoo. Make sure you put the plastic retainer washers with the lip up, under a stainless flat washer. That lip retains the snap on plastic cover dome.