How do courses appear as 'Similar courses' on a course page?

The 'Similar Course' of the Course Ver2 content type field needs to be the same for any courses to appear as similar courses on a course page:

For example, course A and course B tagged both tagged with a code '100XXX' would appear as similar courses on each course page.

The image used is the 'ProfilePhoto' field and need to be 280x185 as shown on:

http://t4.net.marjon.ac.uk/webdev/headscape-designs/coursedetails.htm