If you're looking to activate 4K TokKit, there are a few things you need to do first. First, make sure your device supports 4K TokKit. Currently, only the iPhone 6s, iPad Pro and Apple TV 4K support this feature. If you have one of those devices, head to the Settings app and navigate to General > About. Here, you'll see an entry for Maximum Supported Video Resolution. If it says 2160p, that means your device is ready for 4K TokKit.
Once your device is set up for 4K TokKit, open the app and sign in with your Apple ID. Then, go to the video quality settings and select 4K. This will enable 4K streaming on all compatible devices connected to your account.