Freeway doesn’t allow you to apply more than one named (class) style to an object using the user interface, but if you know the existing class applied to an item, you can enter two or more classes manually using the Extended interface. Click once on the element so it shows its corner handles, then choose Item / Extended from the main menu, and click on the
(or other tag name) rather than the
tab. Click New, then in the Name field enter class and in the Value field, enter your space-delimited list of classnames: button hvr-float.