If your currently hold a student visa and your spouse or partner is not included as a dependent, it is possible to add them to your student visa application.
The criteria to being eligible to add your defacto partner or spouse to your student visa is that you must be able to prove that you are either married, or can show you have been in a de facto relationship with your partner for at least 12 months, or can show you live with your partner.
Try downloading and filling up form 1436: Adding an additional applicant after lodgement from Immi website. Thanks