It is not uncommon for students to get stuck for ideas when confronted with an essay to write. This is particularly true for postgraduate students since at this level students have to decide on the topic and focus of the essay themselves. Undergraduates are nearly always guided by being given the topic and title.
Remember that you will have an assignment to write at the end of each module, so while you are learning about the subject through your lectures and seminars and so on, highlight what interests you in any articles you read during the course of study.
When it comes to choosing your topic, think about what interests you, and then about the question you will ask and how you might answer it. For a module assignment, it is unlikely you will be doing any primary research yourself. This is what is expected for the dissertation. However, you will have to explain why the topic you have chosen is important and also establish the context, for example, how the question fits into what is happening in your own country. This could be the point at which you need an intensive brainstorming session. Think about: what you already know (from previous reading, tutors, own experience), and where you can find resources (for example, searching online databases for your subject).
There are many ways of brainstorming. Using a mindmap is quite common (there are several free mind-mapping websites if you do an internet search). Once you have brainstormed, you can start to group your ideas together and this will be the beginning of your outline. Look at the mindmap ideas in this one for the writing advice part of this website: