I voluntarily signed parental rights it was not court ordered, what is the process to get my children back?

How long ago? Where are you located?

First, unless a court ratified the agreement, it is probably not legally valid. But for us to help you we need to know more about what happened. We need to know when this happened and the general locale. We need to know if you are the father or mother. We need to know who the children are currently with. We need to know why you signed this paper. And anything else that you might think pertinent.