A wool cowboy hat is made out of felt and designed to hold up over time. However, if something happens and your hat loses the shape you like, or you just want to make a couple of tweaks to your wool hat, it can be done with a little bit of patience. Form your wool hat to your head as comfortably as you like, or add a curve to the brim that wasn't there before.
Boil water in a teapot or in a sauce pan.
Hold the area of the hat you'd like to shape over the steam from the boiling water. The steam will make the hat more pliable.
Shape the hat with your hands to look how you want it to. Repeat the steaming if necessary, but don't let the hat get too wet.
Allow the hat to dry completely in the desired shape for the changes to be made permanent.