Start here, the “playground”, and say hello to an AI:
https://platform.openai.com/playground/prompts?models=gpt-4o-mini
Does it say payment information needed, that you need to set up an account “start building” … thus implying you need to first add billing information and making a prepayment?
Your current credit balance to pay for API services:
https://platform.openai.com/settings/organization/billing/overview