Add f6 thru rails-assets and add this to a scss file

app.scss

// Third-party libraries
@import "foundation-sites/vendor/normalize";
// Sass utilities
@import "foundation-sites/util/util";

// Global variables and styles -- Add a global file `app/assets/stylesheets`
@import "global";

// Components
@import "foundation-sites/grid/grid";
@import "foundation-sites/typography/typography";
@import "foundation-sites/forms/forms";
@import "foundation-sites/components/visibility";
@import "foundation-sites/components/float";
@import "foundation-sites/components/button";
@import "foundation-sites/components/button-group";
@import "foundation-sites/components/accordion-menu";
@import "foundation-sites/components/accordion";
@import "foundation-sites/components/badge";
@import "foundation-sites/components/breadcrumbs";
@import "foundation-sites/components/callout";
@import "foundation-sites/components/close-button";
@import "foundation-sites/components/drilldown";
@import "foundation-sites/components/dropdown-menu";
@import "foundation-sites/components/dropdown";
@import "foundation-sites/components/flex-video";
@import "foundation-sites/components/label";
@import "foundation-sites/components/media-object";
@import "foundation-sites/components/menu";
@import "foundation-sites/components/off-canvas";
@import "foundation-sites/components/orbit";
@import "foundation-sites/components/pagination";
@import "foundation-sites/components/progress-bar";
@import "foundation-sites/components/reveal";
@import "foundation-sites/components/slider";
@import "foundation-sites/components/sticky";
@import "foundation-sites/components/switch";
@import "foundation-sites/components/table";
@import "foundation-sites/components/tabs";
@import "foundation-sites/components/title-bar";
@import "foundation-sites/components/top-bar";
@import "foundation-sites/components/thumbnail";
@import "foundation-sites/components/tooltip";