How to choose and modify switchable parts

Question: How to choose and modify switchable parts?

Answer:

In the green room, click the 'Hinges ' Tab.
If there are available part choices for this object, there will be two drop-down menus located under the group 'Part Choices.' (Note that if you're working with an actor object, you'll find additional groups of options listed prior to "Part Choices."
If there aren't any part choices available for this object, then the header 'No Switchable Parts' appears in the same place.
Assuming the object you're working with has at least one part choice, click on the left drop-down list to select the appropriate part, then select from among the options appear in the right drop-down list.
As soon as you select an option from the right drop-down, the object display is updated with your new choice