Its a petty simple system. Down at the bungie labs there are millions of hamsters running on wheels. Each player is assigned a hamster. If your hamster runs faster than all the other hamsters in the party, you rank up. If its the slowest, you rank down. Even if you won. The cutest hamster gets MVP.- Some random BNet person.
Its too early to input the code, they don't have it ready for download yet, try it in a few weeks when it gets closer to the release date, it'll work then.