If you installed a fresh WordPress blog system on your website ,before writing new posts, you will need to remove the sample pre-installed comments, blog posts, etc. This can be done in the following way:
1- Login to your WordPress admin dashboard.
2- Under Dashboard Menu, hover your mouse on Posts and click on All Posts.
3- Hover your mouse on the Hello World post and the Trash option will appear. Click it to remove the post.
4- Now do the same with the sample page by pointing your mouse on Page in the Dashboard menu and then choosing on All Pages.
5- Choose Comments from the dashboard and then the Trash option will appear. Now click on it.
After you take these steps, your blog will be clean, without sample posts and comments, and you can start blogging.