Please note that this article is for the new projects overview screen. If you have not yet transitioned, please see http://ask.leanstack.com/team-management/how-do-i-add-guest-members-to-a-project
You can manage collaborators directly in the projects overview screen as seen below:
Each project maintains it's own project team and you can manage them individually by clicking the button next to the list of current collaborators. This will open up an edit panel which gives you access to manage existing collaborators and invitations. From here, you can also send invitations.
When sending new invitations, you can select the type of role you wish that user to have once they accept it. Members have full access to the project. Guests have view only access. When you click "Send Invitation", the individual will receive an email with details on how to accept it.
Please note that adding members to your project will also automatically add them to your organization. If you have a paid subscription to LEANSTACK this will increase the number of seats toward that subscription.