In fact, you cannot ask this question like this. In fact, a better way to ask is, "How does one use 'in fact''? or "How can you use the expression 'in fact'? "how to" is not a question. In fact, this is a common error by many English learners. While it seems ok, as the phrase is common in English, in fact, it is only used differently. I can answer in this way, but in fact, I do not know how to answer better. :)