Do as much of the work in your windows browser as you can. That means uploading images, filling in all the fields on the forms etc. Next, copy your app to your iCloud drive as that’s the easiest way to find it on the MacInCloud. Lastly login to iTunes Connect (I have it on my IPad but I can’t upload from there but use it to familiarize yourself with it.) It usually takes me about 15 on MacInCloud but has taken an hour. Oh, also make sure you’ve built with the distribution certificate and provisioning profile.