You'd definitely have to enrol. The enrolment process is you accepting that offer. Once you're enrolled you'll have to fill out a form from the faculty regarding the deferring.
what I want to do is delay the start of the offered degree a little later cause I'm still not too sure if I want to leave my current degree or if something else comes up, so what do I do if it's this situation?
So how does he accept his offer? If he hasn't enrolled the that means he hasn't accepted his offer and if you haven't accepted your offer how can you defer?