if you have a one lever delta faucet and spout, everything goes through the center hole and the two side holes mount the faucet to the bowl with nuts. for ease of installation get a "basin wrench" and possibly a ratchet wrench with a one foot extension and appropriately sized sockets. the feed lines accept a 3/8" flexible line(s) from your angle or straight stops under the sink - [shut offs for the water]
if you have two faucets, separate cold and hot spigots, then each valve installs in its own hole with a 1/2" pipe sized nut that holds the faucet in the hole. Again you'll need a flexible feed line with a 1/2" NPT nut on one end and a 3/8" compression fitting on the other.