Connect your "hot" pigtail to the black wire in the ceiling and the neutral pigtail to the white wire from the ceiling.
I recommend installing the 3" screws (or whatever size you need based on your housing) to your mounting plate and fitting the housing over these. You will need to install the acorn nuts and then keep turning them until they hold PVC housing tight against the ceiling. If you do it this way you need to make sure you insert the machine screws into the threaded holes in the mountain plate.
That's it. I love this unique light fixtures and gotten lots of positive feedback. Hope you enjoy it as much as we do.