how does a 600 get back to a 1200
How did you get from 1200 to 600 to begin with. The only way I see that could have reasonably happened is if you were a new player on this site and you lost a few early games. The site adjusts initial elo and just a few defeats would have seen that elo plummeting.
Instead of worrying about getting to 1200, first try and learn. Once you play better chess your rating will increase gradually.