If you are setting up a payment form with Authorize.Net, you must provide the API Login ID and Transaction Key to set up the integration. Both of these can be obtained from your Authorize.Net account. Below are the steps:
1. Log in to Authorize.Net’s Merchant Interface, and click the Account tab. You will be redirected to the main Settings page.
2. Under Security Settings, click the API Credentials and Keys option.
3. On the next page, copy the API Login ID.
4. Under the Create New Key(s) section, select the New Transaction Key option. If you wish your old keys to be unusable, check the Disable Old Transaction Key Immediately option. Otherwise, leave it unchecked.
5. Click the Submit button. You will be asked to verify your identity with a PIN. The PIN will be sent to the email address associated with your Authorize.Net account.
6. Once verified, the new Transaction Key is displayed. Copy the key before clicking the Continue button or closing your browser.
Related Article: How do I obtain my API Login ID and Transaction-Key.