You create data type objects simply by calling their constructors with appropriate arguments, and possibly filling in additional properties that were not passed into the constructors. For example:

StructuredDataType structuredDataType = new StructuredDataType(
        "ControllerConfiguration",
        "urn:UnifiedAutomation:CppDemoServer:BuildingAutomation:ControllerConfiguration")
    {
        new DataField("Name", UAOpcBinaryStandardDataTypes.CharArray),
        new DataField("DeviceAddress", UAOpcBinaryStandardDataTypes.UInt32),
        new DataField("TemperatureSetpoint", UAOpcBinaryStandardDataTypes.Double)
    };

Notice the use of pre-defined primitive types from the UAOpcBinaryStandardDataTypes Class. It is common to encounter references to standard data types from OPC Binary data type system, and the OPC UA Complex Data extension gives you this class so that you can refer to them easily.