Just follow the directions that come with the walking foot. If you have trouble at that point, ask here. Most walking feet require you to put them on so that the arm on the right side of the foot "embraces" the screw that holds the needle in place. It can be a bit tricky to get all the angles right so that you can do this, but it can be done.
A generic walking foot doesn't always work as well or do as many things as a walking foot designed specifically for your machine, but sometimes the generic foot works out really well. You just have to try it to see.
I would advise *not* trying to do reverse stitching with a generic walking foot. Also be careful about needle positioning before you start sewing; the needle usually needs to be in center position with a generic foot.