Select Multiple Options from a many-to-many relationship

I’ve created a many to many relationship between two modules, however I’m not able to make a multiple selection. How do I go about do so?

There must be “SELECT” button on subpanel to select many recrods on each module.

There is a select button on the sub panel. But for example I want to add one to person to two different department. The department is going to change when I add the person to another department. Instead of showing two departments.

How do allow many to many relationship to be shown in the list view?