At minimum you would need something like this in your VTL file:
{
"selector": "textarea",
"plugins": [
"advlist anchor autolink lists link charmap print preview hr anchor pagebreak searchreplace wordcount directionality",
"visualblocks visualchars code fullscreen insertdatetime nonbreaking save table contextmenu textpattern",
"emoticons paste textcolor colorpicker textpattern validation compat3x spellchecker media"
],
"content_css": [
"/path/to/css/file.css"
],
"body_class": "wysiwyg"
}