Prerequisites

To begin using Xcode, you need to have a valid Apple developer ID on their portal. This application also requires an iPhone since it uses the camera module. You need to have the provisioning profile assigned to the particular device. Only then should you be able to build and run the application on the device. 

You can clone the complete TensorFlow repository, but to run this application you may not need the complete source code. If you have downloaded it already, you don't need to do it again:

git clone https://github.com/tensorflow/tensorflow

Xcode comes with command-line tools, as shown here:

xcode-select --install