As an organization owner or project board admin, you can add an outside collaborator and customize their permissions to a project board.
An outside collaborator is a person who isn't explicitly a member of your organization, but who has permissions to a project board in your organization.
In the top right corner of GitHub, click your profile photo, then click Your profile.
On the left side of your profile page, under "Organizations", click the icon for your organization.
Under your organization name, click Projects.
In the projects list, click the name of the project board.
On the top-right side of the project board, click Menu.
Click , then click Settings.
In the left sidebar, click Collaborators.
Under "Search by username, full name or email address", type the outside collaborator's name, username, or GitHub email.
In the search results, click the correct username and click Add collaborator.
Optionally, next to the new collaborator's name, use the drop-down menu and click the desired permission level: Read, Write, or Admin.