In order to build and share your Custom App, you will need to first create an Apple Developer account.
To get started, visit developer.apple.com/programs/enroll/
Things to note:
This process requires a $99 annual fee.
If you have a D-U-N-S number, you will need to enroll as an organization (this is the method we recommend). If you do not have a D-U-N-S number, you will need to enroll as an individual.
Learn more about D-U-N-S numbers here!