I want to reserve an app name that I intend to build out over the next 90 days, how do I do this in apple\'s web developer portal?
Go to iTunes Connect, then Manage Your Apps, then Add New App.
Create an App with placeholder data (you'll need screenshots, real or temporary).
If you don't upload an associated production [App Store] distribution App within 90 days, you'll lose the right to use that name forever.
Cyber-squatting on an App name you don't make use of is bad form.
If you decide you don't want to use the name, please delete it and free it up to someone who will.