Obtaining a Civil Annulment is similar to obtaining a divorce in that, you must file a petition with the courts stating what grounds you feel the marriage should be annulled. In most cases of Civil Annulment the marriage is of short duration and normally there is no issue of splitting marital property, child custody or child support.
However, there are instances of long-term marriages ending in annulment. If this is the case then distribution of marital property, child custody, child support and alimony are handled in the same way the would be if the marriage ended in divorce.
Whether you are in a long-term or short-term marriage, the process involves filing a petition requesting the marriage be void and a hearing before the courts. If the courts find that the petitioner, the party requesting the annulment has proven their case the marriage will be declared null and void by a judge.