Alright so I finally hit the upper league, Woo-Hoo!... Now what?

I play co-op almost 99% of the time, and everything that comes up talks about "GO TO QUICKMATCH, AND LEVEL UP". Basically I hope that co-op works just fine for league points, because I would like to compete in the rankings, but I hate quickmatch so much, but we'll see. I haven't even played one match and I'm already in awe and wonder about this new League system and how it works.

So if anyone is an expert on this or know of a website or something laying it out, let me know. Thanks