What asset?
You will not be able to find a “step by step tutorial” for that entire one specific thing; break it into pieces and work on that instead:
- do you have a basic understanding of the engine? variables, framework, functions, communication?
- do you have an NPC?
- can you make the player speak?
- do you have the dialogue / VO lines?
- can you show widgets for the text? (if subs are needed)
- if this a one-time behaviour, you can hard code it; if there’s more dialogue - you will need to develop a dialogue system
- do you have animations ready for lying down and sleeping?