how do you have a divorce dismissed

You can file an agreed Motion to Dismiss (signed by both parties).  However, if no action is taken on the case, then the Court will eventually set the case on its dismissal docket.  If no one shows up for the dismissal hearing to argue as to why the case should be retained on the docket, then the Court will dismiss the case without need of any further action by the parties.  Keep in mind, the downside of waiting for the Court to dismiss could mean months and months of waiting.  The time frame is different for each Court depending on the Judge and the Court's docket.