Thanks for the feedback. We have already investigated the video, and our colleague has provided the right information for plugin setups based on our docs. You see, this plugin setup consists of many steps, and it is really important to follow all of them carefully, the same way it is being mentioned.
These are the two components you need to follow through, in order to setup the plugin properly:
Based on your video, you have remained at the 6th step from the Plugin API Configuration section. Please note that it is best to have 2 separate pages for success and error cases of your Sign in with Apple process. You can set any name pages you prefer, but it is important to separate them in the Endpoint settings.
Regarding Service ID, you simply need to create one and configure it with your redirect URL you want your customers to land on after a successful signup.
Hope it helps.