To secure a modification of a previously set child support obligation you must establish that there has been a significant, permanent change of circumstance since the child support issue was lasted reviewed (his support was last set). If at the time his child support was last set he was unemployed and little to no income was imputed to him, the fact that he has secured a new job and is therefore earning more should serve as the "change of circumstance" you need in order to justify a review and likely modification of his support obligation. To get the ball rolling you need to file a Motion with the court. Within that Motion you should account for any and all relief you are seeking, i.e. if he has amassed child support arrears you want to address that in addition to resetting his current child support obligation. Forms for such a Motion are available online at the New Jersey Court's Website.
If you can find the means, you may be best served by retaining an attorney who will know how to dot all the "i" and cross all the "t" as you not get multiple chances to do this right, i.e. if the support is not properly set now you may be hurting your chances of securing the proper support award in the future.
Kenneth A. White, Esq.
The Answer provided was based on the limited information provided, and represents information based on the law in general, not a legal opinion that can be relied upon. Before a formal legal opinion can be offered I would need an opportunity to review all possible relevant facts and circumstances. You cannot rely on the advice of an attorney given over the internet. The exact facts of your sitaution, including facts which you have not mentioned in your question, may completely change the opinion that is being offered. Please be aware that the above comments are neither protected by attorney-client privilege, nor may the same be the basis for a malpractice lawsuit.