Does your machine take side clamp feet? If so, then there is no way to attach these. It's not uncommon for feet to get paired up with a machine they don't belong to. There is a wide variety of top clamp feet too, and for the most part they are not interchangeable.
Side clamp presser bars have a flat side, and the top clamp attachment fits on a round presser bar.
I believe Free/Westinghouse is threaded, but I'd have to go look to be sure. I know one of them is.