How to prove a notarized agreement is valid in the court of law

I have filed case under sec 138 & my case is on hearing stage . I have submitted all the evidence in the court but one evidence which was an agreement between both of us ,was not submitted at first stage but later on when I submitted this agreement in court , it was allowed by court on condition that I have to prove this document is genuine . Sir I want to bring it to your notice that this agreement is notary registered . so sir I have two questions . 1) How can we prove this document is genuine in court ? 2) can notary registaar help us in proving this document in court ? .