The key terms in this essay are 'managed' and 'effectively' so when answering this question it's important to have these words in the back of your head.
Like any History essay, you should follow the acronym PEEE (Point, Evidence, Explain, Evaluate) in every paragraph. In the introduction you should outline what themes you want to cover in the essay- giving context to the question is often a waste of time and won't gain you marks. The best way to tackle this question is to look at themes across the period and look at Bismarck's management of nationalism through these themes and see if there was a figure who managed it more effectively.
So an example of themes would be: politically, socially, economically and militarily. If you were to answer the question in this way then each paragraph would focus on one of these themes and discuss other key figures who impacted politics, society, the economy and the military.
In the conclusion, which should be a substantial length given the breadth of the question, give some form of overview on the period and explore other themes that you didn't cover e.g. the role of intellectual ideas.