You can add a new post by hovering over “Posts” in the sidebar and clicking “Add New”
or
You can click the “Posts” section in the sidebar to see all of your posts, and then click “Add New” at the top of the page.
However, if either of those things isn’t there at all, try checking to see if there’s a users section in the left hand sidebar. If there is, click on “Users”, then on your account. Scroll down and make sure that “Role” is set to “Editor” or “Administrator”
Hope this helps.