Understanding Gemini API documentation

Question

I am trying to understand Gemini API for my Flutter project. However, in the documentation, I do not understand this "In the VS Code Extension Development Host window, write in a code comment describing the user interface component you want to generate".

In VS Code Extension Development window, I could not find any option to write "code comment". You can check this documentation Gemini API documentation

Anybody can help me understand it? Thanks.