Authorize setup? OpenCart ver 1.4.9.1

I'm using OpenCart ver. 1.4.9.1 and setting up Authorize (AIM), I would like help in setting up 3 fields
1) Login ID ....is this the username that I use to login to admin with?
2) Transaction Key ...if it's not my password from the login to admin then where do I get the Transaction Key
3) MD5 Hash ...where do I get that?
This is all new to me and it's been great so far setting up except ...the payment.
Thanks in advance for any help

Login name
from your authnet account under settings
from your authnet account under settings

Is this in the OpenCart Administration? If not do I need to set up an authnet account somewhere else?

You can get the Authorize.Net payment gateway and a merchant account from SaleManager. US merchants get a FREE payment application for the iPhone, BlackBerry, Windows Mobile and Google Android smart phone! For more information visit http://salemanager.com/authorizenet.html