The pool builder should tell you how to start up the pool. Another option that may be offered is to pay them to have someone start up the pool for you. I did the latter which insured the builder could not say it wasn't done properly, but honestly the guy they had do the start up had no idea what he was doing at all. He did do all the brushing for me, but he NEVER tested the water. He just occasionally added some liquid chlorine and once he haphazardly dumped a bunch of stabilizer into my skimmer basket. Once his start up was done, I took over and got the pool in balance. It may not be the same for you, but the biggest thing for me is that pH wants to skyrocket, I'm constantly adding muriatic acid to the pool. Make sure you get something in writing from them if you do the start up on your own, so you know how to manage pH. Different builders sometimes want different pH levels during the first few weeks.