It sounds like you are doing great things! I'm glad we have people like you who are willing to do the very difficult jobs to keep us all safe. This is something you can get very inspired about. If it is important to you that you are prepared for emergencies, prepared to be a leader, and doing something meaningful for your job, then the theme for your essay can be a concept associated with what drives you to do this kind of work.
What drives you to do this instead of accounting or teaching middle school? Why do you choose this?
I think you will do well if you start with a topic sentence. Write a sentence that succinctly tells what your plan is for the next year. Then, develop it into afull paragraph by elaborating and the giving an example.
Next, give a topic sentence about what you would like to be doing 5 years from now. Then elaborate and give examples so that it becomes a full paragraph.
Finally, give a topic sentence about this school or program to which you are applying. Elaborate, and grow it into a paragraph.
Go back and write an intro paragraph.
Go to the end and write a conclusion paragraph.
Post it here so we can help!
Google "topic sentences" just to make sure you know what they are.