This is a good question. There are several important points to keep in mind when writing a history paper.
First, you have to know your material well. This is to ask, what are your sources? There are two types of sources. You have your primary sources and then you have your secondary sources. You should start with the primary sources, as these are the basic data. Secondary sources give you ideas of what other have done with the primary data.
Second, you need a thesis statement. All good history papers have a point that they want to prove. So, what do you want to prove? This is your thesis.
Finally, make sure that you have some good reasons for your thesis. These are your body paragraphs.