Generate the API Login ID and Transaction Key. From the Authorize.net main menu, click on theAccountlink. This will take you to the account Settings page. From this page, locate theSecurity Settingssection, then click on theAPI Login ID and Transaction Keylink. Follow the instructions there. Make a record of the Login ID and transaction key, and store in a safe place. You will need these values for your website(s).
From yourAdministration Area, click onTools -> Payment Settings.Enter your Authorize.net API Login ID in thePayment Processing IDfield, and your API Transaction key in theProcessing & Confirm Passwordfields.
Important: The API Transaction Key is a unique string that identifies your account. When a new Transaction Key is generated all websites and applications that currently process with the old Transaction Key must be updated!
Once this information is in your administration area, please run yourtest transactions.