how to add more then 8 sims to a household?

I'm afraid there's something missing here. There are no NRaas > (command) entries that show up like that unless you use HotKeys. We have to specifiy the mod being used, in this case MasterController, first. So NRaas > MC > Add Sim.

MC has a setting in its options that must first be switched on first to allow for Greater Than Eight.

There are six NRaas mods that allow for overstuffed houses in different ways, many of us have all of them in play anyway. But which ones are absolutely required depends on what the player is trying to do and how they plan to work with them. They are described here.

http://nraas.wikispaces.com/Which%20Mod%20FAQ#Overstuffed

(Disregard any notices about Wikispaces shutting down, we know that and it's business as usual over there until we move to our new site)

And yes, I agree that you can't really move an entire town into one household if we are talking about more than 15 or 20 sims for various reasons and that this discussion should take place on a site devoted to mods, such as at NRaas itself, not here on AHQ.