What's the exact wording of the assignment? It seems to me from your post that it is a summary of the main points rather than putting forward and evaluation, but what do you think?
Getting used to philosophy is just getting used to a new way of thinking. If you stick with it, you'll get it soon enough and you'll start to think in the way they want you to. For now, this assignment is very short (300 words is about 3 paragraphs!) and I imagine it probably isn't worth very much of your final mark and nobody expects you to be a complete genius at it straight away.
Anyway, yes, it's probably most useful to you to think about what are the the most critical take-home point(s) of the philosopher, I would say you'd probably describe between 1-3 points, depending on what you consider to be very important, summarise them, then put the work into the context of philosophy, why they are important to the discipline.