I would be very hesitant to put my legal reasoning in the hands of an LLM. They’re not AIs, they just come up with plausible text completions. There have actually been cases by now of lawyers who’ve gotten fucked by using AI to try to save themselves effort and then it not being good enough for what they were expecting from it.
If you’re convinced you want to do this, there are basic tutorials on Youtube - I’m not 100% sure but I think that instead of “fine-tuning” in the same way you would do to fit an LLM to a problem space, you want to import the legal documents into something like Chroma, then use something like Llama as hooked up to the Chroma DB. But again, I wouldn’t. For messing around with some things it’s fine, but for legal documents you really want a sentient intelligence involved in the process.