If there is a custody order in place you would file a Motion to Modify and then set forth in there everything you want to change.
However, I am assuming they didn't use an attorney in the original case and so he ended up with an order that is causing problems. That is what happens when people try to handle the cases themselves. While there is no reason someone can't do a "vanilla" divorce (no kids, no property) they shouldn't do case involving children or real estate without a lawyer because things like this happen.
He can talk to Legal Aid and see if they can help or he can hire a form service like the one at this link but if there is any way possible he really should hire an attorney. Some of them will allow a payout or the use of a credit card, etc.
This is one of those cases where you can see the other side is going to be a problem and it is likely to require multiple hearings.
However, a motion to modify is the tool to use to get the order changed.
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