My child lives with me, but the court papers state that his mom has timesharing/custody. How do I get legal timesharing/custody of the child?

You will need to file a supplemental petition for modification with the court, which you will assert those circumstances which constitute a substantial change from your prior court action to justify you having majority time sharing. That is until you get a court order providing you majority time sharing. Your wife’s status will trump the reality that’s occurring. This is important because it implicates potential payments of child support.