New users can be added on a project-level by navigating to the "Members" Tab and entering their email address and role type.

User permissions are also defined at project level in Managed Service for TimescaleDB and called "project members". Each user invited to a project has one of the available roles in it, defined originally by the Admin level user who invited the user to the project. Roles can be managed by a project Admin user under the Project Members page:

Project roles overview
Admin role is required to invite more users to the project or to modify billing information. Admins can perform all available operations for projects and services. Each project must always have at least one Admin user.
Operator role provides full access to services but does not allow modifying billing information or project members.
Developer role allows managing existing services (e.g. creating databases and connecting to them), but does not allow making any changes that would affect billing (for example, starting or stopping services).
Billing contact is the project member whose credit card is used to pay for the project; the billing contact can not be removed from the project.
Operations allowed for each project role
Developer
Access hosted services (PostgreSQL) by using the connection parameters and service URI
Create and modify service databases
Create and modify service database users
Create and modify PostgreSQL connection poolers
Operator
All the operations available to Developers (see above)
Download project PDF invoices
Create and modify services
Start scheduled service maintenance
Admin
All the operations available to Operators (see above)
Delete the project
Invite MST users to the project
Remove users from the project
Define the project role for users in the project
Update project billing information