You can Google it and get more details, but here are the basics.
For a tail, split it open and remove all of the bone and as much fat as you possible can from the skin. The better you clean it, the less likely it is to smell. Lay it out flat and cover it with salt and borax to dry it out. You will want it to dry as flat as possible, so you want to pin it open some way while it dries.
Fly Fishers International certified casting instructor