As an account administrator you can select the active projects on your account, which a user should have access to. Users with the coworker role need to have access to the project to be assigned project tasks and be able to track their work time for a given project.
To assign projects to a user please follow these steps:
Go to Manage> Team.
On the user list, click on the user you’d like to edit.
In the 'Permissions' section select the projects you want this user to have access to.
Note: You can grant and revoke project access to a specific user anytime.