Divorce is the legal end of a marriage. When you void a divorce, you are declaring that the legal decision to end that marriage was either incorrect or improper, and you erase the decision from ever happening. In essence, this means the marriage never ended. This isn't an easy decision to reach, and it will require lots of work and detailed reading of the divorce proceedings to see whether it can even be done.
Contact a lawyer who specializes in divorce law in your area. If you're going to try to get a divorce declared null and void, you will need the expertise of someone who is well versed in the law.
Go over all of the divorce proceedings and the paperwork you received. You need to find a reason to declare the proceedings void, such as improper procedure, misleading actions, threats or something equally valid. For instance, you could declare proceedings void if you could prove that your spouse threatened to take away your children if you didn't fill out the forms. You could also make a case that the divorce was void if the court didn't follow proper procedure.
Keep all court appointments and approve all necessary decisions that your lawyer makes on your behalf. If you want your divorce declared void, your representative will have to file necessary motions, set court dates and open up a new case (or an appeal case). There aren't any specialized forms you can file to void a divorce decision, so you need to let your representative guide you.