This tutorial assumes you've already logged in to WordPress, and will show you how to write a new post.
Click Posts in the left margin.
Then click Add New.
Enter a title for your new post.
Then enter the content of your post.
You can optionally assign this post to one or more categories.
When finished, click Publish.
That's all there is to it! You can now click to see your new post on your live website.
The post is shown here on your website.
Now click the All Posts link.
Your new post is listed here, and it's from here that you can edit or delete posts from your website.