Once you have created your Article content type, navigate to the "Articles" menu item you created (or you can go to the Content Search screen and select "Article" from the Content type selector).
Click on the circle + sign on the top right to add a new Article.
Enter in new Article content - feel free to use lorem ipsum or cut and paste from your favorite news source. Fill in some specific tags and upload an image with the content.
Once you have filled in the fields, hit "Save & Publish" to publish your content live.