This is a very important aspect of how to write essays. Lets say you have 2000 words to write for the whole essay and 5 main points, with 2 subpoints for each. Remember that you will also need an introductory and concluding paragraph, so that makes it about 12 paragraphs in total. This means you will need to write about 150-200 words per paragraph or sub point. Once you start to break it down in this way, you can see that learning how to write essays is not overwhelming - all you have to do is write a short piece of text for each of the ideas you are presenting.