If you are not in agreement with your spouse in seeking a divorce, you must contest the divorce by responding to the Notice to Respondent that your spouse will serve you with.
If you contest your divorce, your spouse may be asked to prove the grounds of the divorce, or give evidence surrounding particular issues (custody or support, for example). At this point, you will be given an opportunity to put forward your case.
A contested divorce can be a complicated process. It is strongly recommended that you contact a lawyer to represent your best interests.