i just redeemed my codes and connected the API and recieved this error message

429 You exceeded your current quota, please check your plan and billing details. For more information on this error, read the docs: https://platform.openai.com/docs/guides/error-codes/api-errors.

I havent used it yet. When I go to Chatgpt it isnt clear on how to add credits. Can you help with this? Also, how can we get an estimated costs of monthly fees