How do you get Wolf on Super Smash Brawl for Wii? I didn't get enough information last time.?

I've heard that once you complete the Subspace Adventure of whatever it's called, you go back to it and there's this floating door or something. I don't know where exactly it is, there's so many places and I need to know the name of that exact place. Also if there's any other way to get Wolf too. I have some comprehension problems so a lot of details in the answers would be very helpful :)