After being successfully registered in a developer’s testing program, the developer sends you an archive containing two files: the application and a provisioning profile. You need to install both files into iTunes to be able run the application on your device.
After opening the archive: Publishing Applications for Testing
1. Drag the provisioning profile to the iTunes Library group.
2. Drag the application (the file with the .app extension) to the iTunes Library group. The application appears in the Applications list.
3. Sync your device.
If the version of iPhone OS on your device is earlier than the test application can run on, you need to update your device with the current release of iPhone OS.