Prompts are how you tell your LLM what to do, here’s how you can do that in popular frameworks
https://docs.llamaindex.ai/en/stable/examples/customization/prompts/completion_prompts/
https://python.langchain.com/v0.1/docs/modules/model_io/prompts/quick_start/
Certain open-source models need special formats for their prompts, for those you can refer Ollama Modelfiles for reference