First export all the data from WordPress.com
Buy a hosting.
Then go to Godaddy and point the nameserver to your hosting.
Login to yourdomain/cpanel
Click on "fantastico"
Click WordPress from left hand menu
Click on "New Installation" ( Under the big heading "WordPress")
Now Do the Following:
Install on domain: Select Your Domain Name
Install in directory: Leave blank
Admin access data: Type a Username and Password
Admin Nickname: Put yourname or admin
Admin e-mail (your email address): Your email ID
Site name: Type your site name
Site Description: Tag line
Done. click install WordPress and then finish installation.
Log in : go to yoursite.com/wp-admin
type the admin username and password.
Change the permalink structure.
Import the database.