After all of your readings are at zero - you should add your clean up crew of snails & hermits.
Fish should ideally be added 1 at a time with the most aggresive added last. You
should be QT'ing the fish before adding them to the tank for about 3 weeks to be sure they are disease free, or you may find yourself dismantling your brand new tank to get the sick fish out of there for treatment.

Before adding corals, you want to be certain your other parameters Ca, Alk & Mg are where they should be.
Most of all take your time and have a PLAN of what fish & corals you want to keep. Not all fish & corals get along.