When you register your Livescribe smartpen through Livescribe Desktop, the registration process prompts you to create a Livescribe account. If you need to, you can also create an account manually without registering (or even owning a Livescribe smartpen).
You can manually set up a Livescribe account either from Livescribe Desktop or directly from a web browser. To set up a Livescribe account from a web browser: