Automattic announced today that it has added .CO as a new top-level domain option for WordPress.com users. This joins other options like .ME, .COM, .NET, and .ORG. It will cost you $25 a year for a .CO domain.
To register for a .CO domain, go to Store and Domains in the dashboard, and type in the .CO domain you wish to register in the "Add a Domain" field.
After that, it will ask you for more details, such as contact info, and if you want to add Private Registration to the purchase (an additional $8), then you will register the domain, and make your payment. Once you go through all of that, you'll activate it by going to Store and Domains in the dashboard, and selecting the button next to the domain, and clicking "Update Primary Domain."
According to Automattic, over 1.5 million .CO domain names have been registered in over 200 countries since 2010.