totally new 72 gallon bow

i have a new 72 gallon bow tank everything from the stand up is entirely new. I need to be schooled, i installed the eshopps over flow pf 800, and the eshopps rs 100 sump, along with a octo nwb sss 110 skimmer. I tried to match everything up. I think it's pushing 800 gph. I'm far from knowing anything hence the name no clue. I put about 70 lbs of LR. i also added 30 lbs of a shell sand mix. I'm in the battle full swing with no clue? i can't even figure out the nitrate nitrite nitra na bla bla bla bla i'm lost. I'll take any simple advice except stop now!