There are two settings you can choose from and they can be changed any time:
Private to Project Members: you will have to manually add members to your project before they view it.
Public to the Organisation: all members within your organization can view it.
Changing Settings from the Teams page
Click on the Settings icon in the top right corner of a project card.
Under the Project Settings section, click on the settings you would like for the project.
Changing Settings from within a Project
Click on the Settings icon in the left navigation bar.
Select Project Details.
Click on the settings you would like for the project.
Next Up: Creating a Project