Silverbucket's instructions and documentation has moved to a new address:
You can add new users by following these steps
1. From People tab click "Add a person +" button.
2. Fill in information for the new user and click Save.
You have now created a new person. When the new person logs in for the first time he/she must first reset the password.
Instructions for how to reset your password can be found here.
Watch also video: How to add people