It depends on why it warped, and how much you care.

The safest thing to do is to get a nice plank of unwarped wood and use the existing fuselage as a pattern to cut out a new one.  Then burn the old one.

I did (once) straighten one out by moistening it then holding it with the opposite bow for a while.  But that was a fuselage that had been straight and had acquired a bow through mistreatment.  And it was probably a stupid idea anyway.

You could straighten it using steam, then glass or carbon veil it to strengthen and keep it straight.