If the defendant is willing to accept service, then it means s/he is willing to accept a copy of the summons and complaint directly from you.  The defendant must sign the original summons where it says “Acceptance of Service” in the presence of a notary public, and you must then deliver the original summons signed by the defendant to the court as proof of service.  You can often find a notary public at a bank, and most attorneys are also notary publics.  The notary public may charge a small fee to witness the defendant’s signature.