In the WordPress Admin click on Posts in the left hand menu.
You can also click the arrow (circled above) to open the Posts subpanel.
Click “Add New” to add a new Post.
On the New Post screen:
1) Add a title
2) add content by copying and pasting from a document or writing into the Visual Editor. The Visual Editor functions like most word-processing software, so it should be familiar.
3) Choose a Category
4) Click Publish
Check published version of the post by clicking the “View Post” button.
If there is a problem, return to the the recently published Post. Modify the recently published post by changing any of the text or changing the category and then click the “Update” button.
This video explains almost everything you need to know about adding a post: