[A]ll iOS builds need to be signed by a developer certificate and a provisioning profile, that is tied to your Apple developer account and the device you wish to test on.Source: https://build.phonegap.com/docs/ios-builds
This was quite a process! Thankfully, it was well documented. I've outlined my steps below.
1. Obtaining a Certificate
To request an iOS Development Certificate, you first need to generate a Certificate Signing Request (CSR) utilizing the Keychain Access application in Mac OS X Leopard.
2. Assign your Device
In order to debug your iOS application on an Apple device, a Team Agent or Team Admin must first enter the Unique Device Identifier (UDID) for each iPhone and iPod touch into the Provisioning Portal.
3. Create an App ID
An App ID is a unique identifier that iOS uses to allows your application to connect to the Apple Push Notification service, share keychain data between applications, and communicate with external hardware accessories you wish to pair your iOS application with.
4. Create a Provisioning Profile
A Provisioning Profile is a collection of digital entities that uniquely ties developers and devices to an authorized iOS Development Team and enables a device to be used for testing.
Continued in part 3...