DO have vs have

Hi

i have studied one story like this ’ i do have to tell something to you ’

But i have little confusion as which is correct 'I do have to tell something or I have to tell something

“Do” is used for emphasis there.

e.g.

I like cheese.
I do like cheese.

I do like a natter*.
I do like a good natter.

Visit us when you’re in town, won’t you?
Do visit us when you’re in town.

natter = verb: talk socially without exchanging too much information