My experience with electives. If your electives are apart of your course, i.e. doing Law Electives in a law degree, then you only need to fulfill the prerequisites (that is have completed the units it has asked for). The enrolment process is the same.
However if the elective is not on your campus or is from another school or programme you will need authorisation from your head of campus for your degree and possibly check with the unit coordinator (this can be done over the email). You simply put this info on the enrolment or adjustment form and everything falls into place. its a simple process.