Get Started
If you haven’t already, create a WordPress.com user account and blog at https://wordpress.com/start
Export
In your old self-hosted WordPress.org site, go to Tools → Export and download the .xml (WXR) file to your computer.
Import
To import the .xml file WordPress blog into your current site, go to My Site → Settings and select Import from the Site Tools section at the bottom.
Click Start Import next to the WordPress importer.
Drag your .xml file into the box, or click the box to browse to the file on your computer.
Once the file has finished processing the uploaded file, click the Start Import button. You will be asked to reassign the authors of the imported items to an existing user on the new site before starting the import process.
Note, if you had more than one author on your site and wish to keep your content assigned to the same authors: invite the user to your site on WordPress.com prior to import. This will allow you to assign the posts to the correct author. Inviting the users will require they have a WordPress.com account.
Check
Check that all of your content and images have been moved over to your new site.
Domain Mapping
Connect your domain name from your old site to your new WordPress.com site with Domain Mapping.