Creating a own AI model

I need to create a model like chat gpt for which is trained for my own data. I cannot give the data outside that is the reason. How to do that??

download or use free llms models and modify it to your data.
refer library
https://www.langchain.com/

Thanks
I there any specific tutorial created to train my data. For those free models. It is somewhat difficult to do that

I cannot understand how to train it to a particular dataset, my own data set