Have is a very overloaded word in English that has a few very unrelated meanings.
One of those is to have X Y, it means
cause X to do or complete Y
how X is caused to do Y is not defined and is up to whoever is doing the "having", but forcing X to Y is typically not implied (if it is, you'd say make X do Y instead of have X do Y).
Have your brother call me.
This means to cause "your brother" to "call me."
Ways this could be accomplished: you might ask your brother to do that, or you might be in a business setting and assign him this as a task.
This sense of have is often used as an imperative.
Have X with no Y. used as imperative, typically means "consume, eat, or enjoy X". If X is food, this is common.
Have some french fries.
Don't use this when X is a person because it could have erotic implications. If you don't know what Y is in have X Y, say something like this:
Have Jon do it / this / that / something / anything.
Have Jon do whatever is needed.
Have X in the sense of I possess X isn't usually used imperatively to mean I'm asking you to possess X. You typically need to use get X or take X instead.
I have 3 dollars.
Take the 3 dollars / Get the 3 dollars.
Though someone who has a bunch of dollar bills in their hand and is waving them around and giving them away might say Have 3 dollars.