public string URL {get; set;}

{
    // Create a connection to the WMS server
    var serverConnection = new CIMProjectServerConnection
    {
        URL = "URL of the WMTS service.xml",
        ServerType = ServerType.WMTS,
    };
    var service_connection = new CIMWMTSServiceConnection
    {
        ServerConnection = serverConnection,
        LayerName = "AdminBoundaries", // Specify the layer name you want to add
    };

    // Add a new layer to the map
    var layerParams = new LayerCreationParams(service_connection);
    layerParams.MapMemberPosition = MapMemberPosition.AddToBottom;
    //Note: Needs QueuedTask to run
    var layerCreated = LayerFactory.Instance.CreateLayer<FeatureLayer>(layerParams, map);
}