Your avatar is automatically retrieve from gravatar.com. To add/update your avatar please update it at gravatar.com.
Click on your avatar and choose "USER PROFILE" from the menu
On the next page you will see a button to change your own password
If you are an admin on your account you can add new users or edit existing ones.
To add a new user go to the Admins page and click on "ADD NEW USER" button on the top right of the page.
In the popup that open after that you can set the Name, Email and password of the new user and optionally you can make them Admin. Note that new users still have to verify their email before being able to use their account.
Hover on any user in the admin page and you will see a menu that allows you to edit or delete the user.
When editing users you can change their Name, Email or Password.
You can also set or remove their admin flag.
Hover on a user in Admin page and click on the delete icon. You will receive a confirmation pop up before deleting the user.