Favourited courses are personal to your account. You only see the courses you have favourited yourself. There is no limit to how many courses you can favourite.
To add a course to your favourites, select the star icon on the course thumbnail.
Your favourited course will then appear at the top, under 'Favourites'. This can be useful if your institution subscribes to many courses on Boost.
To remove a course from your favourites, click the star icon again.