I would also like to know this. This is exactly the kind of AI-assisted stuff I want to do, but no matter what I try, I just can't seem to get any information about how to actually get access.
Use AI Dungeon. It's the same thing just wrapped up into a webpage. AI Dungeon tries to steer you into using GPT-3 for dungeon crawling but you can edit the prompts, text, responses, anything. I used it to simulate a paper on curing Covid.