There is another thread about walking feet on FWs. Check that out. You can buy them at sew-classic or the April site. Be sure it says it's for a FW because the feed dog are narrow on the FW and you want the foot to line up.
You put them on the machine just like any other foot except there is a fork arm that you put over the thumb screw that holds the needle in place. That fork will go up and down with the take-up lever and allows the walking foot to work properly.
I bet there is a utube or something out there that will show you how it works. I'm not good at finding those but someone here will post one I bet. Good luck with what you find.