If I already have custody with one child in place how do I add another to the same case ? File a motion or fill out a whole new custody paper? Where can I go for someone to help fill them out?

When you file the new case they will ask about previous cases. If it is one continuous case the clerk will assign the same case number. I know when I filed for my kids previously having a case for our older child they statrted a new case but the new case will include both children.

Go to the family help center to get the necessary paperwork, and ask if you can add the children or ask for an additional child or children to be added to your custody