Deploying and Testing an iPhone App on Device

It involves the following steps (most of which requires access to the iPhone Developer Portal):

1. Creating a development certificate signing request and have it signed at the Developer Portal.
2. Register the test device on the Developer Portal.
3. Create an App ID on the Developer Portal.
4. Create a Provisioning Profile on the Developer Portal.
5. Download the Provisioning Profile file. Double-click on it and it will be loaded into the SDK tools. It will be possible build and install the app onto the device with XCode from this point.

The steps are also explained here:
mobiforge.com/developing/story/deploying-iphone-apps-real-devices

Note: article based on SDK 2.2.1 so not every step is identical.