To give a simple example, the configuration to get info about your own channel looks like this:
If you do not know how to find out the correct endpoint, look to YouTube’s API documentation and browse for, e.g., Channels: list.
Choose one of the predefined use cases, for instance, list (my channel), and switch the example to CURL.
The endpoint is under # HTTP URL:, where you omit the base url https://www.googleapis.com/youtube/v3/.
You can use other Generic Extractor’s functionality too, including nesting. This example downloads your channel, iterates through its playlists and gets all their videos: