Measure your casings leaving 1/4 of an inch top and bottom.
Order bones for each casing according to measurements.
I tend to get mine here http://www.corsetmaking.com/CMSpages/CMShome.html
You can get your busks, washers and Grommets here as well.
Slip your bones into their appropriate casings until you have them in
with 1/4 and inch of fabric above and below each bone.