Converting a regular Order to Auto Order

There isn't really any simply way to change an order from a standard one to an Auto Order. However, there is a workaround. Basically you will place another order for the individual with "test" Credit Card information so the customer doesn't get charged a 2nd time. A test order simply skips sending the payment information to you payment gateway.  Once completed, you enter their real credit card information so the subsequent auto (recurring) orders will charge appropriately.
To begin, have a copy of the original order handy so you can re-enter information on the new order. Make sure you have all the credit card information.

1. Set your Payments Configuration into test mode:
Log in to your account and navigate to:

Click on the "new" button at that screen. Click on the Credit Card radio button and enter any valid credit card number. Click on the SAVE button.
Note: Notify your fulfillment company (if exists) to NOT ship the incoming order (give them the details of the order).

2. Complete the purchase:
Purchase the Auto Order item with the same customer information as the original. When prompted, enter the credit card that you configured at the Payment Test screen. Finalize the order and write down the order ID or print the order. Since you configured a test Credit Card number, the payment process will be skipped.

3. Remove the Test Processing configuration:
As soon as you have finished the order, remove the TEST Payment configuration you configured in Step #1. Failure to do this will cause any subsequent orders to be processed without the Credit Card being charged.

4. Locate the order and set a valid Credit Card:

In order for the customer to be charged for subsequent Auto Orders, you'll need to enter the customer's valid credit card information. To do so Log in to your account and navigate to:

At the search screen, enter the Order ID and click the "Search" button. When the order appears, click on its order ID link. The order will appear on the screen with a new set of menus at the top. Click on the "Edit Customer Info" link. At the next screen you will be at the "Billing" tab. Replace the TEST card information with the customer's real Credit Card information. It's also a good idea to enter some notes in the "Merchant Notes" field indicating what took place. Consider adding notes to the original order also.

Click on the SAVE button at the bottom of the screen to complete the process.