Getting back to where you were when you opened the link you got in email. In the blue column on your left, you want to click the posts button. You click on it and choose the first option which is all posts. In the upper right corner you will find a button that says add new. You've got to click here.
Your screen will look like the one when you make a new page. The title of your blog can be entered here. Just below the title you enter the text of your blog And finally, click the button that says publish and you are done.
You also have the option to choose between private or public. As the name implies, a private post is not visible to the general public. It can only be viewed by those who have access to it
With the public option everyone that visits your site will be able to see your blog.