Add a checkbox on the upload page which is turned off by default.
When turned off the forward button should be Validate and result in file validation with default settings (the first profile from the list) right away.
When turned on a Configure step should be added to the stepper and the button should become Configure leading to the settings page.

Please make sure not to duplicate code on Configure and Upload page which is responsible for triggering validation, put it into some common control/constant/... so that it was simply reused.