Add usage example instructions use case, such as `phi-3-mini-4k-instruct` to `phi-3-mini-256k-instruct` ?

[lh0x00]

Firstly, this paper is really really impression. This resolves one of main issues của currently LLMs.

But I have many confused, maybe because I don't really welling in this field. So, I have a question for my case: I want to ft phi-3-mini-4k-instruct use my own datasets at 4k, then I want to extends context length to 256k.

Can you give me a instructions or code example ? Finally, many thanks for all.