I am trying to upload an app to apple store and this is my first time. I am currently using Transporter when I try to upload an app I keep getting errors “Asset validation failed. Missing or invalid signature. The bundle ‘Uk.companyname.app’ at bundle path ‘Payload/Runner.app’ is not signed using an apple submission certificate”

I am trying to upload an app to apple store and this is my first time. I am currently using Transporter when I try to upload an app I keep getting errors “Asset validation failed. Missing or invalid signature. The bundle ‘Uk.companyname.app’ at bundle path ‘Payload/Runner.app’ is not signed using an apple submission certificate”