Text from their Facebook page states:
Enter for a chance to win round-trip coach-class airfare for travel to Chicago, Madrid, Rio, or Tokyo in the Where I've Been Olympic Twitter Giveaway. All you gotta do is:
1. Follow Where I've Been (@whereivebeen) on Twitter.
2. A message will be posted by @whereivebeen at 9am CT on Thursday, October 1st. Tune in and RE-TWEET THAT MESSAGE!
Winner will be selected at random & announced on the @whereivebeen Twitter page on Friday, October 2nd.