We use "have to" to express obligation or necessity, such as children having to go to school or an employee having to take the bus to work. We can also use "have to" in questions to check if something is required. Additionally, using "don't have to" indicates there is no obligation or necessity, for example not having to work on Sundays or eat disliked foods.

1. 
We use have to to say that something is
obligatory or necessary.
e.g.
Children have to go to school.
My dad has to take a bus to work.

2. I
You
We
They
have to wear a uniform to
school
He
She
It
has to clean that room

3. 
Do
Does
have to wear a
uniform to school?
Yes, I do/ No I, don’t
I
You
We
They
He
She
It
have to clean that
room?
Yes, he does/ No, he doesn’t

4. 
We use it to express that there is no obligation or
that something is not necessary.
e.g.
I don't have to work on Sundays.
You don't have to eat anything you don't like.
Mike doesn’t have to take the kids to school.