After preparing your app on App Store Connect and downloading your IPA, you can submit it to Apple. Please note that Apple can answer 3 weeks later and you have to have a Mac.
- Download Transporter with this link (from a Mac)
- Connect with your IDs
- Click on ADD APP and select your IPA
- Wait until Transporter uploads your IPA file. A green check logo appears.
- To finish, click on Done
Congratulations! You have just uploaded your app to App Store Connect. The final step explains to you how to submit your app on Apple.