One or both of the spouces file a request to the court, in which you ask for a court decision on all relevant issues, such as alimony, division of assets and pensions. You need a lawyer to file this for you. The application for divorce must be served on the other party by a bailiff.
When there are children involved, a parenting plan is required by law. The court will ask the other party to respond and will discuss the positions of the parties during a hearing in court. When parties have signed a divorce agreemente (and parenting plan) a hearing in court won’t be necessary.