Styling the Field Wrap of a Ninja Form

nf-css-field-wrap.css

/*
Styling all field wraps
*/
.field-wrap {
  /* Your CSS styles */
}
/* 
Styling a field type wrap
EXAMPLE: .textbox-wrap {}
*/
.field-type-name-wrap {
  /* Your CSS styles */
}
/* 
Styling a specific field wrap
EXAMPLE: #nf-field-12-wrap {}
*/
#nf-field-field_ID-wrap {
  /* Your CSS styles */
}