Under the Users menu, accessible from Settings>Users, you can create and manage multiple users on an account. You can update your account profile or change the password on a user account. The user menu option is not available on the free and basic monitoring plans, but there is the option to edit an account profile or change a password under those plans. Furthermore, the free and basic monitoring plans are limited to one user per account.
You're able to add multiple account users to your account. When adding a New User, you have the option to add users to multiple contact groups, as well as send weekly uptime reports via email. Under Actions, you're able to Edit a user account.