Space Wolves w/ Grey Knight Allies(newbie?)

Hello and thanks for the help. I just played my 1st battle. Wow, why have I waited so long. I am a veteran gamer , loved the models but never played.
Well, a few grand later and that's old news.

I am building a Space Wolves Army and want to supplement it with Inquisitors and Daemon Hunters/Grey Knights. I know it says they can allie but then it also says you can't use Grey Knights. so does that mean exactly what it it says, that I can't use 2 squads of Grey Knight troops that I want to? It's the whole reason I got them, I love they way they look..

I also want to use Capt. Stern. Is it possible if I have a 2000 point army?

so very confusing to me. I did a search but still unclear. any help would be much appreciated.
Cheers