See Also
To prepare a module for use in a hierarchy, you need to decide which variables in the module get their values from other modules, and which variables in the module (if any) output the module's results. In most cases, you explicitly indicate which variables are module inputs and which are module outputs by Defining Module Inputs and Module Outputs.
When you're ready to use the module in a hierarchy, you need to assign each module input to an actual variable. To make variables available for assigning to a module input, you first need to make explicit connections (with connectors) between the module and other modules, or between the module and a variable in the model. Once those connections are established, you can assign module inputs.
You can also use the Ghost tool to connect variables. Using the Ghost tool allows you to automatically assign module inputs and outputs as well as make connections between modules and other modules or variables.
Define variables as module inputs or module outputs