some chlorine needs to go in pretty much immediately, to avoid any algae growth.
Then adjust pH- you need to know the current pH to know whether to go up or down
use Muriatic Acid to lower pH, use borax to raise pH- shoot for 7.2-7.6
Some CYA if it's outdoors
Everything else you can adjust later, as you get the water fully circulated and filter online, etc...