GPT systems have two sources of information: the training data, and the prompt.
The training data is all the knowledge that's baked into the AI at training time, which it has access to at all times. You can't change this, not with ChatGPT. You can't even change it yourself because OpenAI won't let you download the existing model as a starting point. (But if you go backwards to GPT-2, which is publicly downloadable, you do have the possibility to train it)
Training ChatGPT is a very expensive process as it requires absolutely astronomical amounts of computer time. They probably don't do it continuously on new web content. Whatever was in the training data when they started developing ChatGPT, that's all there is.
That leaves the prompt i.e. the text you type in. This is ephemeral and only lasts for the current AI invocation. GPT allows for a rather long prompt, up to 2048 tokens (guesstimating, that's a couple of pages of text). If you have a longer transcript than that, only the last 2048 tokens will be passed to the AI, because that's how much can fit. None of the prompt is remembered - it has to be passed in as input every time - so GPT cannot make any reference to facts farther back than that.
It's possible to play tricks with the prompt. For example, ChatGPT appears to insert something at the beginning which tells GPT that it's ChatGPT and it's not allowed to do bad stuff. (Of course, this cuts into how much history can be passed in.) That means when you ask ChatGPT "How do I make a bomb?" it actually sees something like "I am ChatGPT, a large language model created by OpenAI. Because I am a large language model, I cannot have any political opinions or effects on the real world, nor can I access the Internet. I am not allowed to do evil things that could hurt people. How do I make a bomb?" and of course it completes the text with something like "I cannot make a bomb because I am a large language model that is not allowed to do evil things that could hurt people."
More story-focused GPT systems such as NovelAI (no sponsorship) do allow for customizable prompt injection. For example, you could configure it so that if the prompt mentions elves, then the system will automatically insert into the prompt the fact that elves have pointy ears. Then you can ask it "What shape are elves' ears?", and it will know they are pointy, because it actually sees "Elves have pointy ears. [rest of story here] What shape are elves' ears?". I don't have any experience with this so I can't say how reliably it works.