Parentage may be established at the time of birth or later when the mother and father of the child execute an affidavit of parentage. The affidavit of parentage form was updated in October 2013--more than a year after the enactment of the Revocation of Parentage Act.
Everything you need to know about completing and filing the form is here: Download Instructions.Affidavit of Parentage These instructions also give you information about how to obtain a copy a party's copy has been lost or mislaid.
A form that is fillable (that you can use the computer to complete) is here: Download Affidavit of Parentage.FillableForm
A form that you can complete with a pen is here: Download Affidavit of Parentage
Be sure to save the fillable form to your computer prior to completing it so that you may save the form once it is completed. If filled out online, the information will disappear when you close the form.