This can be managed in different ways depending on the instructor's preference.
To assign projects to students directly, an educator can click on the project under the Projects tab of their course page, and click "Create Team." This will invite students to the appropriate project by email, and will form their teams for them.
More commonly, instructors will provide students with instructions to sign up and access the Projects page themselves. To find these with your unique course code, go to the Students tab of your course page and click 'Invite Students.' Students will be told offline (or in their LMS) which project they are assigned to. Students will see the option to start the project and create their team themselves.