There are many ways to write about data. The table on the left lists some roads you can pursue.
Whatever your approach is, your audience should be a major drive to how you write about data.
The overall structure of a data analysis report is simple:
The writing should be as "unremarkable as possible" - overly formal or casual, metaphorical, technical. It should be simple and focus on the procedure or outcome, not the process, and not be too broad or narrow (again, consider audience).