Begin with a clear introductory paragraph. Share the with the reader at the outset the direction you intend to follow in your essay, highlighting your thesis and how you intend to defend it. Use separate paragraphs for major points. Remember to begin each one with a clear topic sentence. Support your assertions with detail.
Data is always important to the historian.
Because your time is limited, assume the reader's knowledge of your subject, but be sure to explain the connections between the evidence and your assertion and emphasize clearly the significance of your point. Don't forget a brief concluding paragraph. One or two sentences will do. If it can't be read, it won't help you. Double spacing always makes messy handwriting more legible.