Split it in staves around three inches wide and pull the two best ones out and seal the ends with two coats of shellac and put them in the attic for two years. Take the other two and take off the bark and sapwood and chase down to one ring above the one you want. Seal the ring on the back and the ends with two coats of shellac. Lay out a bow and rough it down to almost bow dimension using drawknives, hatchets, rasped... Whatever you are comfortable with and then bring it in the house for a few months. That's a start.