At the bottom of this help page is more information about the program, and exactly where to look for it as a setting in your overall organization or in individual projects you select to ensure it is enabled and confirms your enrollment – if you are eligible.
You must deliberately choose the option to share prompt and response training data with OpenAI.
https://help.openai.com/en/articles/10306912-sharing-feedback-evals-and-api-data-with-openai
You can review the particular eligible models, as not all qualify.
There is no display in the main billing usage page that shows how much you were not billed for complementary use.