To enable the Transaction Details API:
Log on to the Merchant Interface at https://account.authorize.net .
Select Settings under Account in the main menu on the left.
Click the Transaction Details API link in the Security Settings section. The Transaction Details API screen opens
If you have not already enabled the Transaction Details API, enter the answer to your Secret Question, then click Enable Transaction Details API.
When you have successfully enabled the Transaction Details API, the Settings page displays.