Doesn't the blu-ray player have an internet input? You would plug your LAN connection there or a usb wireless modem in its USB slot. When you start the Netflix application, it will ask you to verify your account through the internet by your computer/laptop. Instructions should be self explanatory from there.
all you need is a lan line (cable) going from your router to the bluray player and it'll show up on your network and you'll be able to connect to netflix, bluray live, or whatever else you want to connect to. The usb is for files; you don't have to plug in a wireless modem, it's internet ready just not wireless so you do need the lan cable.