This is one way to ask a friend or acquaintance to do something social. For example:
You'll have to come over and visit us sometime.
You'll have to send me a copy of that. (When looking at a photo someone took)
Use this expression for fun social things. Don't use it to talk about something that a person has to do for work or for large requests.
When you pronounce this phrase, don't put stress on "have to". Put the main stress on the verb, and a little stress on "you".