Use the tool buttons Add Input Port and Add Output Port to create an arbitrary number of input and output ports.
In contrast to hierarchical modules, where you can define only single input and single output ports, it is possible to define multiple input and multiple output ports for primitives. For each port definition, MLDesigner generates an entry in the primitive source code upon saving. These port items cannot be changed in the primitive source file, but must be changed using the Property Editor. Select the port object and change the values of the port properties.