Take a quick break and a deep breath before you go back to your document and start refining what your users really need to know about it. Think about their context: how are they coming to this page? What do they know about the product at that point, and what is the minimum they need to know before they are able to move forward?
Honestly, the first step is a quick brain dump onto a white, empty text file. Think of each paragraph as a module, and each sentence as an element you will eventually add to your design. The exercise of writing down everything you can possibly say about that product can help you organize your thoughts before you start prioritizing the most important talking points.