As a practicing tutor and essay service editor I have seen many essays in my life, so I can give you some pieces of advice on how to write them.
1) Look through other
essay examples, there are plenty of already written ones on the web, go through them, try to find key points that are similar, and to understand the structure.
2) Write as many as you can on various topics, professionalism comes with experience, the more you write- the better it gets.
3) Don`t stuck. If you are writing an essay and at some point, it starts to go really slow and hard and all the appropriate thoughts are floating from your mind just take a rest. Maybe even concentrate on another essay on a different topic, letting the ideas come again.
4) Follow the rules, you have the requirements, you know the structure, you are aware of key phrases and words, just follow them all and always check your essay after writing for
spelling mistakes, grammar ones, misunderstandings, etc .
Wish you luck!