Now my question: - What is the path to the page that allows me to edit the configurations outlined below?  I am trying to use my own stylesheet and have it appear in the dropdown

Please check the Editor.EditorBodyStyle and EditorWysiwygModeCss property. 

Editor.EditorWysiwygModeCss Property
Specifies the location of the style sheet that will be used by the editable area. Multiple Style Sheets are supported. Example EditorWysiwygModeCss="example.css,~/portal.css,/default.css"