The following outline is for guidance purposes only.
You should write a draft of your introduction very early on, perhaps as early as when you submit your research proposal, to set out a broad outline of your ideas, why you want to study this area, and what you hope to explore and/or establish.
You can, and should, update your introduction several times as your ideas develop.
Justify the use of each data source (e.g., trustworthiness, credibility, reliability, validity).
Also explain how your data sources fit with one another (e.g., complementarity, development), how they contributed to a sensible overall view of the consequences of your change effort.
Show how your action design was informed by published scholarship.
What theoretical lens(es) did you use to shape your overall action research.
What was your position as an insider in your work setting?
Make a case that improvement was needed in your topic area and in your organization. Cite data, where possible, that supports your claim that the need was real and urgent in this setting.
Keeping the introduction in mind will help you to ensure that your research stays on track.
The introduction provides the rationale for your dissertation, thesis or other research project: what you are trying to answer and why it is important to do this research.