Philosophy of History as a class in university is normally something you would take alongside your other history (or related) stuff in order to pad out your understanding and help you read and study history.

Philosophy of History classes will normally be a selection of philosophy topics chosen for their relevance to the study of history and the humanities generally. These courses are usually designed to equip you for further study in the humanities.

Philosophy of History is not a separate subject to either history or philosophy, not really, it is the parts of philosophy your professor(s) think are most relevant to a history course.