I expected to flop hard online but I'm actually good even though I just got it. I guess cuz everyone else sucks as much as me.
When you first turn on your Wii U, You'll see the little orange friend icon. Click on it and then just type in their User ID. You've probably already figured this out by now tho.
I played it alot yesterday with friends (offline and online) and i noticed that it is really hard to get to the fron when you are among the last, just because you don't get that good items