You are able to add as many users as needed to your team and with certain plans you have the ability to specify user roles and restrictions, as well as restricting user access to projects.
In the app navigate to users in the sidebar, click the add user button at the bottom of the users list. Note: if you have a lot of users already you might need to scroll down to see the add user button. Enter the users name, email address and and the users role within the organisation. Click send and an invite will be sent to the users email address.
Click the cog icon in the users table and you will be able to delete a user.
There are 3 main roles in the application and each have a different level of access.
Owner - The owner is the user that setup the team, and has full access to all areas including billing plans etc, only team owners have the ability to create and delete admin users
Admin - Has majority of the same abilities as team owner except the permission to create admin users and manage billing and plan settings
User - Has the lowest level of access, and can only manage project content.
Advanced user permissions are available in pro plans