If you were married in north carolinea and lived in Ga. for 15 yrs.divorced in Indiana.

If the divorce decree in Indiana addressed the issue of the children, then you could simply for a modification in the divorce decree to address support.  If however, it was never addressed you may need file where the non-custodial parent is located.  If that is the case, then I would highly recommend you utilize the services of a child support office as they have great interstate procedures set up to assist with getting support established in another state.