To purchase tickets for DrupalCon Chicago, you first need an account on the DrupalCon Chicago site. If you already have an account on Drupal.org, then you can use that account to log into the DrupalCon site. This account will be used to populate the fields in the Personal Information section of the registration form, though you will be asked to provide some additional information.
You will then be asked to select any pre-conference training sessions you might like to attend. Training sessions are either $350 or $450, depending on the session.
After that, you will be given the opportunity to purchase a Drupal Association membership ($30) and additional tickets for the official after-party at the Field Museum of Natural History ($20 each).
Finally, you will be given the opportunity to verify your registration and enter payment information prior to confirming and submitting your order. You will then receive confirmation of your order via email.