We are looking to write a scientific paper in the topic of measurement physics, that includes experimental data and dimensional analysis. How do we begin the process of writing a paper for a journal, maybe Physical Review Letters?
In answer to the question you need to find books about academic publishing. also, many scholarly journals have their own guideline for publications. Best if you read all you can about the academic publishing process to improve your chances to be published. try also to look at answers in the Academia StackExchange.
If you are not speaking about research papers but textbooks you need to familiarize yourself with non-fiction publishing, there are many books on this subject too.
In answer to the comment many people who have done only a master, or even a bachelor can later, and often do, contribute to the body of scientific literature. Even in PhD programs, some get more advice than others and a PhD holder may not know how to publish. This is even more true for international degrees whose study-contents may not include papers or research publications at all.
Also, like it may be the case here, he is asking about writing a paper for his professor. many people involved in reseach may have to write the paper for their "elders", specialty lab or research assistants, even if they are just students. From the tone of the question, i would guess that the asker is starting his PhD program.