The English/EAL exam is always a bit tricky to prepare for because, well, how to you study a skill?
My answer to that is this: you don’t. You practise a skill. That is, you repeat an action until you can do it perfectly. And then you repeat that perfect action another million times.
This means you should take out your past essays, read the feedback your teacher/tutor has given you, then rewrite the essay/paragraph. This is why I often ask my students to rewrite sections of their essay because there’s no point in writing terrible essay after terrible essay. All you’re practising is writing crap. The only way you get better is by learning from your mistakes and finding better ways to write what you’ve already written.
I hope that helps!