These models are not yet free, but OpenAI plans to make them available to everyone. Until then, the only way to access o1-preview and o1-mini is through one of the paid subscriptions, including ChatGPT Plus, Teams, Enterprise, and Edu. Developers can also access through the API.
ChatGPT Plus is the best way for individual users to access the models; it costs $20 per user per month and comes with other perks, such as priority access to the latest models and the ability to create GPTs.