Are you facing Blog.php already exists error on creating a new blog page in the page manager?
If yes, then you need to open your Cpanel or FTP connection.
Under the HostX template directory, you will find Blog.tpl file. You need to rename that file to make a custom blog page in the page manager.
Please Note: Once you created the new blog page it will not work with announcements. You can create your custom blocks under that page.