To log into your email account you can go to http://gmail.com and log in with email@example.com or go to http://mail.google.com/a/d12aa.org and log in with just your username. If you are already logged into a different gmail.com account, click on your name and then Add Account, you can be logged into both accounts at once. As soon as you log out of one, you’ll be logged out of both. You can look here for help.
Then click on Forwarding and POP/IMAP. Google requires that you approve the forwarding of mail from your other account. Be sure to keep District 12’s mail in the Inbox or mark it as read, it will be of value to the next person that rotates into your service.
It would be best to reply to email from your d12aa.org account. If you choose to respond to mail from your other email account, be sure to CC your d12aa.org account, to maintain the thread for the next user. Encourage contacts to continue to use your d12aa.org account for district business. You may be able to set your email up to automatically send email forwarded from d12aa.org with the Reply To: set as your d12aa.org mail account.
You can also access your d12aa.org gmail directly on your phone. See http://www.google.com/mobile/mail/ for options.