If there is agreement between the parents about who the children will live with and the amount of time the children will spend with the other parent, this can be entered into a Parenting Plan which is a written agreement. If you require legally enforceable orders you should document the parenting plan in the form of consent orders filed with the Family Court.
When there is no agreement as to some or all of the arrangements for the children on separation, you will need to attempt mediation (some exceptions apply) as a first step before you can file an Application for parenting orders in the Family Courts. Alternatively you should consider engaging in Collaborative Law to resolve the dispute.