To create a new blog post just log in to your WordPress admin and navigate to Posts > Add New. You can assign a blog post to categories and you can add tags to your posts. Tags are essentially keywords that are relevant to your post.
If you wish to set your homepage to display your blog posts navigate to Settings > Reading and set the “Front page displays” setting to “Your latest posts”.
If you don’t wish to have your blog posts on your homepage all you need to do is create and publish a page that you would like to be your blog page. Then navigate to Settings > Reading, set the “Front page displays” setting to “A static page” and select the page you wish to be your blog page from the “Posts page” dropdown. If this page isn’t already in your navigation menu, then go to Appearance > Menus and add it.
By default your blog page will display the posts in order of most recent to least recent. The reason for this is so that people visiting your blog will see the most recent post first rather than having to scroll down to the bottom of the page.