In your web browser, visit https://platform.openai.com/

Click the "sign up" link. Then, you can use your e-mail to sign up, or an existing Google or Microsoft account.

OpenAI may require additional steps such as e-mail or phone verification before you can log in to your account.

Once you have completed the verification process and logged in, you will next create an API key. Use the menu in the far upper right corner (probably labeled "Personal") and then select "View API Keys".

Then, create a fresh API key by clicking "Create new secret key".

Save this secret key to use later in the next step.

At the time of writing, OpenAI provides a free credit with new accounts. After the free credit is used or expires, you'll need to enter a credit card in your billing information to keep using the service.

Using the project tends to cost a few cents per session at most, and it's easy to limit your monthly bill to a pre-set amount such as $8.00.

To set a hard usage limit per month, visit the "Usage Limits" section of the OpenAI website.