Login in to your Store Manager
(a) Login to your E-store by using your username and password:
(b) Under the "Main Functions", click on the "Store Manager" link.
(c) After clicking on the "Store Manager" link above, you will be taken to a section where your e-store(s) will be listed. Click on name of your e-store as shown below to enter the management area.
(a) After clicking on the name of your estore in the last step, you will see a screen as shown in the screenshot below:
(b) Under the section "Payment Gateway Options", select Order processing via "Authorize.Net".
(c) Click on the "Update Store" button at the bottom of the screen to move to the next step.
(d) In the next screen, select your payment options as shown in the screenshot below.
(e) Now enter your Authorize.Net login and the transaction key that you obtained in step 2.
Click on the "Finish Setup" button at the bottom of your screen when you are done.