Add roles to users
As a project creator, you can add a role to a person. To do that, visit the person's profile (go to "Users" to see the complete user list and find and click the one you want to add), scroll down to "Project & creator roles," click the "Creators"/"Projects" tab and "add creator roles"/"add project roles."
NOTE: Creator roles will give access to all projects of this creator, while project roles will give access only to a specific project.
Below, you'll see all roles enabled for this person. You can edit or remove this at any time.
Alternatively, you can invite a user directly in Users -> User list by clicking "Invite collaborators" and entering an email. You can choose the roles for this user from a list: