You can use these wheel spacers to push out the wheel a bit. Some people do it for the looks and others use wheel spacers because they fit new rims and the new rims catches the calipers. Especially on the Rangers, if you fit the rims of a newer model on an older Ranger the rims will catch the caliper and you have to install a set of wheel spacers.
The wheels spacer bolts onto the vehicle on the existing studs with the nuts supplied. Your wheel then bolts onto the wheel spacer using the studs on the wheel spacer and your original nuts.