Find a communication piece. Title your post with the kind of piece it is (what class it was written for, what the goal of the assignment was, etc.). Then, explain what your piece is about and why you feel it represents your skills in communication.
You should locate for this activity an essay or paper that you wrote for one of your other courses that best represents your ability to communicate in writing. You could reflect on the essays and papers written for other courses and choose one that best fits the criteria of effective communication. You should be looking for things like strong organization, clarity of thought, a clear thesis, and proper grammar usage, for example.