Deploying a react native project using fastlane

I don't usually deploy projects myself, but here I am in this situation where I need to deploy a project built in react native using fastlane.

I am having issue with the line below, any idea what's the --username $DELIVER_USERNAME" should be? is it my appleID or I need to create a fastlane account?

fastlane deliver --verbose --ipa "app.ipa" --skip_screenshots --skip_metadata --username $DELIVER_USERNAME"