Your MA thesis will be the culmination of your work as a grad student, and so you will not be ready to write it until much closer to the end of your program.
However, the more you know about writing a thesis, the easier it will be, and developing the thought processes needed to "think through" a large research project early on will help you with all the research and writing assignments you'll do in your Master's program.
There are a few different ways to begin developing these processes. Some include:
1. Talking to friends or colleagues who have written theses or dissertations and asking them about their experiences. What went well and what had to be altered? What had they wished they had known before they had begun their research project?
2. Making use of published materials on the subject, such as books, that discuss the reasoning behind research techniques used. The more you understand why a certain technique is used or a certain method is preferred in your field, the more informed your decisions will be when you are planning your own research project.
Ikeda Library has quite a few books on thesis and dissertation writing that would be helpful. One book that discusses the underlying thought processes that go into planning a research project also has a helpful supplement of case studies for those who learn best from examples:
Theses and Dissertations: A Guide to Planning, Research, and Writing by R. Murray Thomas and Dale L. Brubaker
Avoiding Thesis and Dissertation Pitfalls: 61 Cases of Problems and Solutions by R. Murray Thomas and Dale L. Brubaker
Both these books are also available as eBooks.
3. Using the IMRD (Introduction, Methods, Results, Discussion) structure, when reading scholarly articles in peer-reviewed journals, to help you locate the author's explanations for his research choices. For example, a researcher will often justify the methods he used in the Literature Review when he is comparing his research project's purpose to those whose projects were similar, or in his Methods section when he describes how this method best suits the population being studied.
In fact, theses have been known to become journal articles! Becoming familiar with the format and organization of ideas in journals in which you might like to publish is a great way to both prepare for writing your thesis, and for sharing it with the world when it is done.