A probate court proceeding may be required to transfer the property, as your parents did not execute a change to the deed when they were alive.
Absent the owners’ signatures on a deed, an order from the probate court order will be necessary to change ownership rights in a piece of real estate. The probate court will also require some type of signed (and preferably notarized) document that prove the intent of your parents to make the deed change: a Will, a Divorce agreement, etc.
You may wish to contact the probate court in the county where your parents died (or where the property is located) and inquire about the procedure necessary to handle this matter pro se.
Or you may wish to seek legal counsel to assist you in this matter; to find a local attorney for FREE, visit Standard Legal’s Attorney Find page.