Log in to WordPress.com and select Import in the sidebar.
You should see this list. If you’re seeing a different style of list, please check out The Alternative Import Page for details.
Click on the “Start Import” button next to the Blogger importer, and you’ll see the import form. Drag your export file into the box, or click the box to browse to the file on your computer.
Once the importer’s processed the uploaded file, click the Start Import button. You’ll be asked to reassign the authors of the imported items to an existing user on your WordPress.com site before the import process gets going.