To create a new post, navigate to Posts in the side bar and select Add New. You will then be brought to the Post Editor, where you can begin by entering a name for the post in the Title Box.
Next, you can write all of your content (or paste it in from another document) under in the Text Editor. When you are satisfied with your text, you can click on Preview in the Publish Box to see what your post will look like.
If there is something you still want to add at a later time, or want to take a break, you can click Save Draft which will save what you currently have, and allows you to come back to the post at a later time. Conversely, selecting Publish will officially release your post to the public, for people to see.