How to add https://api.ebay.com/oauth/api_scope/buy.order OAuth scope to my app

[meakyi_40]

I want to place order on Sandbox environment. But https://apix.ebay.com/buy/order/v1/checkout_session/{checkoutSessionId}/place_order requires https://api.ebay.com/oauth/api_scope/buy.order OAuth scope.
How to add https://api.ebay.com/oauth/api_scope/buy.order OAuth scope to my app on sandbox environment.