On this tab, you can add an eBay Production (live environment) or Sandbox (test environment) account.
Here are the simple steps which you should follow:
Enter a meaningful title for your internal usage.
Select an eBay Account Environment:
You can select from 2 available options: Sandbox – test environment or Production – live environment.
A Production eBay account only works in a live environment. A Sandbox account only works in a test environment. To register for a Sandbox account go to www.developer.ebay.com
click on Get Token button;
you will be redirected to eBay, where you will need to Sign In
next, you should agree with the eBay terms
press Save and Continue Edit button at the top of the page
After saving you will see additional setting tabs under configuration in the left side menu.